event.post uses SDL_PushEvent to add events to the queue.
event.post uses SDL_PushEvent to add events to the queue.

This ensures that if a thread does event.post, it will wake up
a thread blocked in event.wait - previously, this wouldn't
happen.

Fixes #9.

renpy/pygame_sdl2,renpy/pygame_sdl2,renpy/pygame_sdl2,renpy/pygame_sdl2