iOS: Added support for SDL_DisableScreenSaver and SDL_EnableScreenSaver.

include/SDL_hints.h

@@ -243,6 +243,9 @@ extern "C" {
  *  this is problematic. This functionality can be disabled by setting this
  *  hint.
  *
+ *  As of SDL 2.0.4, SDL_EnableScreenSaver and SDL_DisableScreenSaver accomplish
+ *  the same thing on iOS. They should be preferred over this hint.
+ *
  *  This variable can be set to the following values:
  *    "0"       - Enable idle timer
  *    "1"       - Disable idle timer