This threads the netclient session, which avoids timeouts when the
main-thread is not polling (map creation, very long simulation frames).
Unlike the NetServer, which should be as independent as possible from
the main thread, the NetClient is fundamentally tied to the game thread.
Therefore, this only threads the session object.
To ensure good performance and ease-of-use, lock-free queues for
in/out-going messages are used.
This fixes artificial timeouts, while also improving actual ping reports
(since frame-time is no longer a factor).
It effectively reverts D1513/eda236522c and 2e7e1c0b2b, all hacks around
lag-timeouts (and bits of 1a3fb29ff3).
Based on a patch by: Stan
Comments by: Vladislavbelov
Fixes#3700, refs #3373
Differential Revision: https://code.wildfiregames.com/D2848
This was SVN commit r24518.
2d40068cd1