Document SDL_EventFilter and SDL_ThreadFunction

[Quipyowert2]

SDL_EventFilter and SDL_ThreadFunction pages are missing. There are code examples of how to use these function pointers on the SDL_SetEventFilter and SDL_CreateThread pages. The pages link to the pages for the two function pointers but the pages for the function pointers themselves don't exist. I can easily find the typedefs for these function pointers through grepping the SDL2 headers but it would be nice to have some documentation of them on the wiki.

[dustdfg]

Hi @icculus! This issue is solved now