Remove: DOS support

In 10 years there was no active development on DOS. Although it
turned out to still work, the FPS was very bad. There is little
interest in the current community to look into this.

Further more, we like to switch to c++11 functions for threads,
which are not implemented by DJGPP, the only current compiler
for DOS.

Additionally, DOS is the only platform which does not support
networking. It is the reason we have tons of #ifdefs to support
disabling networking.

By removing DOS support, we can both use c++11 functions for threads,
and remove all the code related to disabling network. Sadly, this
means we have to see DOS go.

Of course, if you feel up for the task, simply revert this commit,
and implement stub c++11 functions for threads and stub functions
for networking. We are more than happy to accept such Pull Request.

Remove: BeOS support (deprecated by Haiku)

In 10 years there is no commit to change how BeOS works, and we
have no active maintainer for it. It is unlikely it works in its
current state (but not impossible).

With the arrival of SDL2 (and removal of SDL), BeOS is no longer
support. SDL2 suggests to use Haiku instead of BeOS.

Remove: MorphOS / AmigaOS support

In 10 years there is no commit to change how MorphOS works, and we
have no active maintainer for it. It is unlikely it works in its
current state (but not impossible).

With the arrival of SDL2 (and removal of SDL), MorphOS is no longer
support. There is an SDL2 port for MorphOS, but it is not maintained
by upstream SDL2, and nobody can currently test it out.

If anyone wants to re-add MorphOS, please do (revert this patch,
fix the problems, and create a Pull Request). If you need any help
doing so, let us know! It is not that we don't like MorphOS, it is
that we don't have anyone fixing the problems :(

Update: Translations from eints
finnish: 40 changes by hpiirai
english (us): 19 changes by njn
spanish (mexican): 3 changes by njn

Update: Translations from eints
danish: 11 changes by nielsmh
spanish (mexican): 11 changes by Absay
hungarian: 100 changes by Brumi
russian: 6 changes by Lone_Wolf
croatian: 9 changes by VoyagerOne

Update: Translations from eints
danish: 5 changes by nielsmh
french: 3 changes by glx
spanish (mexican): 4 changes by Absay
russian: 4 changes by Lone_Wolf

Update: Translations from eints
croatian: 4 changes by VoyagerOne
korean: 4 changes by telk5093
russian: 2 changes by Lone_Wolf
german: 4 changes by smwforever45, 4 changes by ShadowCop
spanish (mexican): 2 changes by Absay
portuguese: 52 changes by vesgo
finnish: 3 changes by hpiirai
dutch: 238 changes by JanWillem
estonian: 1 change by rm87

Update: Translations from eints
french: 2 changes by glx
german: 23 changes by planetmaker
danish: 139 changes by nielsmh
spanish (mexican): 3 changes by Absay
portuguese: 55 changes by vesgo
dutch: 214 changes by JanWillem
estonian: 30 changes by rm87

Update: Translations from eints
korean: 15 changes by telk5093
spanish: 2 changes by SilverSurferZzZ
russian: 21 changes by Lone_Wolf
spanish (mexican): 13 changes by Absay

Update: Translations from eints
belarusian: 1 change by translators
norwegian (nynorsk): 1 change by translators
chinese (simplified): 1 change by translators
serbian: 1 change by translators
czech: 1 change by translators
esperanto: 1 change by translators
chinese (traditional): 1 change by translators
portuguese (brazilian): 1 change by translators
norwegian (bokmal): 1 change by translators
swedish: 1 change by translators
lithuanian: 1 change by translators
hebrew: 1 change by translators
croatian: 1 change by translators
bulgarian: 1 change by translators
catalan: 1 change by translators
afrikaans: 1 change by translators
vietnamese: 1 change by translators
slovenian: 1 change by translators
faroese: 1 change by translators
thai: 1 change by translators
frisian: 1 change by translators
scottish gaelic: 1 change by translators
persian: 1 change by translators
korean: 1 change by translators
greek: 1 change by translators
latin: 1 change by translators
welsh: 1 change by translators
galician: 1 change by translators
japanese: 1 change by translators
english (au): 1 change by translators
italian: 6 changes by lorenzodv, 1 change by translators
urdu: 1 change by translators
french: 7 changes by glx
malay: 1 change by translators
tamil: 1 change by translators
spanish: 4 changes by SilverSurferZzZ, 1 change by translators
slovak: 1 change by translators
basque: 1 change by translators
polish: 1 change by translators
indonesian: 1 change by translators
arabic (egypt): 1 change by translators
russian: 2 changes by Lone_Wolf, 1 change by translators
hungarian: 1 change by translators
luxembourgish: 1 change by translators
romanian: 1 change by translators
irish: 1 change by translators
latvian: 1 change by translators
german: 1 change by translators
danish: 1 change by translators
spanish (mexican): 7 changes by Absay
icelandic: 1 change by translators
english (us): 1 change by translators
turkish: 1 change by translators
portuguese: 1 change by translators
ukrainian: 1 change by translators
finnish: 1 change by translators
dutch: 1 change by translators
estonian: 1 change by translators

Update: Translations from eints
russian: 10 changes by Lone_Wolf
hungarian: 5 changes by Brumi
spanish (mexican): 6 changes by Absay

Update: Translations from eints
french: 3 changes by glx

Update: Translations from eints
spanish: 4 changes by SilverSurferZzZ
spanish (mexican): 1 change by Absay

Update: Translations from eints
spanish: 3 changes by SilverSurferZzZ
spanish (mexican): 3 changes by Absay

Update: Translations from eints
italian: 1 change by lorenzodv
french: 29 changes by glx

Update: Translations from eints
hebrew: 22 changes by dnd_man
spanish (mexican): 1 change by Absay

Update: Translations from eints
spanish (mexican): 10 changes by Absay

Update: Translations from eints
spanish: 5 changes by SilverSurferZzZ
spanish (mexican): 23 changes by Absay

Update: Translations from eints
spanish (mexican): 2 changes by Absay

Update: Translations from eints
spanish (mexican): 2 changes by Absay

Update: Translations from eints
spanish (mexican): 1 change by Absay

Update: Translations from eints
spanish (mexican): 1 change by Absay

Update: Translations from eints
spanish (mexican): 25 changes by Absay

Update: Translations from eints
spanish (mexican): 19 changes by Absay

Update: Translations from eints
greek: 46 changes by kyrm
italian: 44 changes by lorenzodv

Update: Translations from eints
malay: 10 changes by eidan_shafie
spanish (mexican): 9 changes by Absay

Change: Use name of cargo instead of Passengers/Mail in town statistics. (#6801)

* Change: Use name of cargo instead of Passengers/Mail in town statistics.
* Cleanup: Remove strings from all language files.

Update: Translations from eints
belarusian: 10 changes by KorneySan
russian: 6 changes by KorneySan
spanish (mexican): 10 changes by Absay

Update: Translations from eints
spanish (mexican): 6 changes by Absay

(svn r27991) -Update from Eints:
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(svn r27971) -Update from Eints:
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portuguese: 41 changes by Samu

(svn r27965) -Update from Eints:
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(svn r27964) -Update from Eints:
spanish (mexican): 10 changes by Absay

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(svn r27960) -Update from Eints:
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(svn r27959) -Update from Eints:
spanish (mexican): 8 changes by Absay

(svn r27958) -Update from Eints:
spanish (mexican): 26 changes by Absay

(svn r27957) -Update from Eints:
spanish (mexican): 3 changes by Absay

(svn r27956) -Update from Eints:
spanish (mexican): 16 changes by Absay

(svn r27951) -Update from Eints:
spanish (mexican): 6 changes by Absay

(svn r27947) -Update from Eints:
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(svn r27946) -Update from Eints:
spanish (mexican): 1 change by Absay

(svn r27945) -Update from Eints:
spanish (mexican): 3 changes by Absay

(svn r27944) -Update from Eints:
spanish (mexican): 1 change by Absay

(svn r27910) -Update from Eints:
spanish (mexican): 10 changes by Absay
dutch: 145 changes by mrLeopold

(svn r27909) -Update from Eints:
spanish (mexican): 4 changes by Absay

(svn r27850) -Update from Eints:
korean: 3 changes by telk5093
spanish (mexican): 18 changes by Absay

(svn r27824) -Update from Eints:
catalan: 7 changes by juanjo
croatian: 4 changes by VoyagerOne
korean: 15 changes by telk5093
scottish gaelic: 54 changes by GunChleoc

(svn r27742) -Update from Eints:
spanish (mexican): 1 change by Absay

(svn r27718) -Update from Eints:
spanish (mexican): 25 changes by Absay

(svn r27624) -Update from Eints:
spanish (mexican): 24 changes by Absay

(svn r27601) -Update from Eints:
spanish (mexican): 4 changes by Absay

(svn r27582) -Update from Eints:
spanish (mexican): 18 changes by Absay

(svn r27569) -Update from Eints:
spanish (mexican): 3 changes by Absay

(svn r27566) -Update from Eints:
spanish (mexican): 6 changes by Absay

(svn r27565) -Update from Eints:
spanish (mexican): 13 changes by Absay

(svn r27563) -Update from Eints:
korean: 1 change by Gimel3830
spanish (mexican): 93 changes by Absay

(svn r27556) -Update from Eints:
spanish (mexican): 36 changes by Absay