The THREADED_EVENTS compile-time define has been replaced with the
SDL_INIT_EVENTTHREAD flag. If this flag is passed to SDL_Init(),
SDL will create a separate thread to perform input event handling.
If this flag is passed to SDL_Init(), and the OS doesn’t support
event handling in a separate thread, SDL_Init() will fail.
Be sure to add calls to SDL_Delay() in your main thread to allow
the OS to schedule your event thread, or it may starve, leading
to slow event delivery and/or dropped events.
Currently MacOS and Win32 do not support this flag, while BeOS
and Linux do support it. I recommend that your application only
use this flag if absolutely necessary.
-Sam Lantinga (slouken at devolution.com)