more or less any input event; fine for the server, not so much use for the
client
* In the main loop, don't bother sleeping if it's going to be less than 10ms as
the methods we're using to sleep at the moment aren't very precise
* Add Sys_PlatformInit for platform specific initialisation
* In win32 Sys_PlatformInit force selection of the DirectX SDL backend in order
to get better fullscreen mouse input (in conjunction with a patched SDL DLL
http://bugzilla.libsdl.org/show_bug.cgi?id=265)
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