Fix bddfcaef: don't tell twice that a client left because of a timeout etc (#8746)

SendError() notifies all clients of the disconnect. This calls
CloseConnection() at the end, which also notified the clients
of the disconnect. Really no need to do it twice.

The status NETWORK_RECV_STATUS_SERVER_ERROR is only set by
SendError(), so in case that is the status, don't let
ClientConnection() send another notification.

Change: move "give money" from client-list to company window

This is a much better location for this button, as you send
money from one company to another company, not from player
to player.

This is based on work done by JGRPP in:
https://github.com/JGRennison/OpenTTD-patches/commit/f82054339124cc6b89c5f4f9dac2d9da62f0108b
and surrounding commits, which took the work from estys:
https://www.tt-forums.net/viewtopic.php?p=1183311#p1183311

We did modify it to fix several bugs and clean up the code while
here anyway.

The callback was removed, as it meant a modified client could
prevent anyone from seeing money was transfered. The message
is now generated in the command itself, making that impossible.

Fix: Thread unsafe use of SendPacket for PACKET_SERVER_MAP_SIZE

NetworkTCPSocketHandler::SendPacket is not thread safe and may not
be used concurrently from multiple threads without suitable locking

Feature #7756: Allow server to supply a reason to kicked/banned clients

This commit adds the missing feature of allowing the server owner to
provide a reason for kicking/banning a client, which the client sees in
a pop-up window after being kicked. The implementation extends the
network protocol by adding a new network action called
NETWORK_ACTION_KICKED that is capable of having an error string, unlike
the other network error packages. Additionally, the kick function
broadcasts a message to all clients about the kicked client and the
reason for the kick.

Feature: Auto-restart loads the original resources again

If the game was started loading a savegame or scenario, auto-restart will load a new random map.
This is inconsistent with the case in which a heightmap was loaded, as in that case the heightmap is kept as a basis for a new game.
This proposal solves this heterogeneity be considering the originally loaded resource shall be kept, hence savegames & scenarios shall be reloaded

Codechange: Replace custom mutex code with C++11 mutex'es.

A conforming compiler with a valid <mutex>-header is expected.
Most parts of the code assume that locking a mutex will never fail unexpectedly,
which is generally true on all common platforms that don't just pretend to
be C++11. The use of condition variables in driver code is checked.

Codechange: Use override specifer for overriding member declarations

This is a C++11 feature that allows the compiler to check that a virtual
member declaration overrides a base-class member with the same signature.

Also src/blitter/32bpp_anim_sse4.hpp +38 is no longer erroneously marked
as virtual despite being a template.

Remove: ENABLE_NETWORK switch

This switch has been a pain for years. Often disabling broke
compilation, as no developer compiles OpenTTD without, neither do
any of our official binaries.

Additionaly, it has grown so hugely in our codebase, that it
clearly shows that the current solution was a poor one. 350+
instances of "#ifdef ENABLE_NETWORK" were in the code, of which
only ~30 in the networking code itself. The rest were all around
the code to do the right thing, from GUI to NewGRF.

A more proper solution would be to stub all the functions, and
make sure the rest of the code can simply assume network is
available. This was also partially done, and most variables were
correct if networking was disabled. Despite that, often the #ifdefs
were still used.

With the recent removal of DOS, there is also no platform anymore
which we support where networking isn't working out-of-the-box.

All in all, it is time to remove the ENABLE_NETWORK switch. No
replacement is planned, but if you feel we really need this option,
we welcome any Pull Request which implements this in a way that
doesn't crawl through the code like this diff shows we used to.

(svn r23817) -Fix [FS#4962]: desync due to different NewGRF version. So reduce the chance that it happens significantly with betas/RCs/nightlies by doing the same as is done for stable releases: check the NewGRF version of server vs client.
Previously this check was not done for nightlies/betas/RCs due to missing versioning information in the source tarballs, but they have that for a while now. So just force the NewGRF version check for all versions, and remove the broken --revision configure option

(svn r22370) -Codechange/fix: keep better accounting of the order in which clients joined:
* Clients can't be starved from joining the game
* Clients will see the amount of clients actually waiting in front of them, instead of the amount of waiting clients in total