Implemented:
	- SDL_SetEventFilter
	- SDL_GetEventFilter
Implemented:
	- SDL_FilterEvents

Also, cleaned up a little the previous SDL_[GS]etEventFilter implementation
Fixed a test function name to make more sense.
Updated TODO file.
Removed the 'data interface{}' stuff since it is really not needed at all in go.
Implemented:
	- AddEventWatch
	- DelEventWatch

There is a caveat, the event watch caching is NOT thread-safe. This is something to watch out for: If a user is adding/deleting multiple event watches and/or getting/settings multiple event filters, synchronization is required.
Fixed formatting
Merge pull request #52 from nlordell/master

Event Filters and Watches