Add: create bundles via CPack

CPack works closely together with CMake to do the right thing in
terms of bundling (called 'package'). This generates all the
packaging we need, and some more.

Add: introduce CMake for project management

CMake works on all our supported platforms, like MSVC, Mingw, GCC,
Clang, and many more. It allows for a single way of doing things,
so no longer we need shell scripts and vbs scripts to work on all
our supported platforms.

Additionally, CMake allows to generate project files for like MSVC,
KDevelop, etc.

This heavily reduces the lines of code we need to support multiple
platforms from a project perspective.

Addtiionally, this heavily improves our detection of libraries, etc.

Codechange: rework how grf and ob[msg] are generated

For grfs, it now uses CMake scripts to do its job, and both grf
files are split into their own folder to make more clear what is
going on. Additionally, it no longer builds in-source (although the
resulting grf is copied back in the source folder).

For ob[msg] it now uses CMake scripts to generate the translation
files; the result is no longer stored in-source (but in the build
folder).

Although all files are available to create the GRFs and basesets, it
won't really work till CMake is introduced (which will happen in a
few commits from here)

Codechange: move regression outside of bin and make it work via CMake script

The tst_stationlist savegame had to be changed to start the correct
AI. In the old setup, all regression AIs had the same name, which
made it impossible to run both regressions in parallel. With the new
setup this is possible.

Although all files are available to run the regression, it won't
really work till CMake is introduced (which will happen in a few
commits from here)

Remove: all existing project files

This prepares for the switch to CMake, which takes over all current
exisiting forms of project files.

Fix: unbreak building with ICU on macOS

A symbol clash breaks building ICU on macOS, and although it isn't
necessary, it might as well be possible.

Fix #8166: don't crash on loading an invalid roadtype newgrf

Initialization code for GRFFile::roadtype_map was copied from
railtype_map. But while RailType is a byte-sized enum and could thus
be initialized via memset, RoadType doesn't have a defined size.

Fix #8024: make online content gui more responsive while loading

Previously the internal content list was invalidated and sorted for
every new item added. Now the sorting is delayed until the GUI is
drawn, which means we only sort once per GUI tick.

Since the amount of incoming items per GUI tick is not controlled by
the GUI but rather by network speed, we were previously doing a lot
of duplicate work per tick, causing the mouse cursor to lag while
the list was initialized.

Update: Translations from eints
croatian: 1 change by VoyagerOne

Fix: Compilation warnings in story_gui and script_story_page

See: #7896

Update: Translations from eints
chinese (traditional): 2 changes by ww9980
chinese (simplified): 1 change by ww9980

Feature: Push-buttons on storybook pages (#7896)

Allow more direct player-initiated interaction for Game Scripts, by letting the GS put push-buttons on storybook pages. These buttons can either trigger an immediate event, or require the player to first select a tile on the map, or a vehicle.

Additionally this reworks how the storybook pages are layouted and rendered, to allow for slightly more complex layouts, and maybe speeding drawing up a bit.

Add: Optional implementation of std::optional for pre-C++17 compilers.

Sourced from https://github.com/akrzemi1/Optional, Boost Software License, Version 1.0.

Codechange: Replace SmallPair with std::pair.

std::pair is already the smallest possible pair, and it already handles non-POD types correctly.

Update: Translations from eints
latvian: 9 changes by Tranzistors

Update: Translations from eints
latvian: 35 changes by Tranzistors

Update: Translations from eints
spanish (mexican): 7 changes by Absay

Update: Translations from eints
latvian: 13 changes by Tranzistors

Update: Translations from eints
indonesian: 1 change by fanioz
dutch: 1 change by JanWillem
latvian: 39 changes by Tranzistors
spanish (mexican): 1 change by Absay

Update: Translations from eints
spanish (mexican): 16 changes by Absay
russian: 3 changes by Lone_Wolf

Update: Translations from eints
latvian: 21 changes by Tranzistors
korean: 5 changes by telk5093

Fix: sdl2-config would always be detected as present

The presence of sdl2-config is used go determine whether to look for
sdl2 first, or just sdl1. However, when sdl2-config is *not* present,
`which` returns an empty string. Due to lack of quoting, this produces
`[ -x ]`, rather than `[ -x "" ]` and it turns out the former actually
has a succesful exit status for some reason.

This was not a problem when just running configure, because it would
then just fail to detect sdl2 and fall back to sdl1. However, when
passing `--with-sdl` (without specifying a version), this would only
attempt to detect sdl2, even when sdl2-config was not present, but sdl1
is.

Adding quotes makes the check work as intended.

Update: Translations from eints
latvian: 45 changes by Tranzistors
spanish (mexican): 9 changes by Absay

Update: Translations from eints
latvian: 54 changes by Tranzistors
spanish (mexican): 4 changes by Absay

Add: INR currency (#8136)

Co-authored-by: ilayarja97 <ilayarja97@gmail.com>

Update: Translations from eints
latvian: 80 changes by Tranzistors
spanish (mexican): 10 changes by Absay

Update: Translations from eints
latvian: 8 changes by Tranzistors
spanish (mexican): 1 change by Absay

Fix: Two issues in MIDI file writer

Variable-length values would write threshold values with a byte too many.
System Exclusive messages would cause write to fail since the end byte was treated as part of next message.

Update: Translations from eints
latvian: 38 changes by Tranzistors

Fix #8102: Update Windows installer strings to reference newer Windows version (#8114)

* Fix #8102: Update Windows installer strings to reference versions newer than 7

* Fix 2c53390: Version strings incorrectly capitalised

Update: Translations from eints
korean: 1 change by telk5093

Update: Clarify some contribution guidelines

Point out that translations should be fixed via the web translator.
Clerify that "changed NewGRFs" means after the game was started, not that any game using NewGRFs is invalid for bug reports.

Fix #8093: Build+Refit changed game-state in command test run, and thus caused desyncs.
Use DC_AUTOREPLACE for actions that shall be reversibe, in this case:
- Do not rearrange free wagons in test-run.
- Do not discard OrderBackups.
The latter was not triggered by actual auto-replace, since it does not set a 'user'.

Update: Translations from eints
welsh: 4 changes by kazzie

Update: Translations from eints
tamil: 16 changes by aswn

Remove: [OSX] Old fullscreen subdriver for pre 10.7 systems.

Since the move to C++11, building for pre 10.7 is not possible with the native
Apple tools. Also, due to bitrot, the file doesn't even compile anymore. While
this could be fixed, it shows that this subdriver is basically never used anymore.

Remove: [OSX] QuickDraw video subdriver used for OSX versions up to 10.4.

Since the C++11 move, getting OpenTTD to compile and run for anything
below 10.7 basically requires building a custom compiler and libc++.
Also, the QuickDraw subdriver crashes on more modern OSX version. While this
is fixable, keeping the driver around is probably pointless.