When the game-loop is very slow, it was easily possible to start
the loop with _shift_pressed being false, but end with
_shift_pressed being true. This doesn't hurt the game as such,
but for the user this can be very weird: I pressed "Buy Vehicle",
pressed shift a bit later, and I still get a cost indication.
Creating a thread was not thread-safe. The irony.
The video-driver has a function GameLoopPause() which first checks
if the thread is the game-thread or not. For this it needs access
to this->game_thread. This variable is set in StartNewThread().
However, due to timing, it is well possible GameLoopPause() is
called from the thread well before this->game_thread is assigned.
And so we have a race-condition!
Simply solve this by preventing a thread to start till we are
done with our bookkeeping.
Prior to this change, road vehicles would always slowdown in curves. This forces the player to build grid like roads. With new height levels and more mountainous maps and in the absense of diagonal roads this causes unnecessary pain. It should be an option to turn this off, so mountainous maps and curvy roads are not punishing the player unnecessarily. Nobody wants to build grid like roads outside of towns.
This makes it easier to spot chunks that have a save_proc that
is a nullptr, but also prevents confusion, where it looks like
the CH_ type of a chunk has influence on how it is being read.
It is not, it is only used for saving.
Basically it is very similar to Vehicles, where there first is
a type field, followed by data of that type. So this commit makes
it looks like how Vehicles solved that.
This removes a lot of custom "keeping track of length" stuff.
This adds two byte extra to those chunks, and might feel a bit
silly at first. But in later changes we will prefix CH_ARRAY with
a table header, and then this change shines.
Without this, we could still add headers to these chunks, but any
external reader wouldn't know if the CH_RIFF has them or not. This
way is much more practical, as they are now more like any other
chunk.
