ios: Move animation callback to its own typedef.

docs/README-ios.md

@@ -225,7 +225,7 @@ Game Center
 
 Game Center integration might require that you break up your main loop in order to yield control back to the system. In other words, instead of running an endless main loop, you run each frame in a callback function, using:
 
-    int SDL_iOSSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
+    int SDL_iOSSetAnimationCallback(SDL_Window * window, int interval, SDL_iOSAnimationCallback callback, void *callbackParam);
 
 This will set up the given function to be called back on the animation callback, and then you have to return from main() to let the Cocoa event loop run.