Renamed SDL life cycle functions

This maps better to how SDL delivers the events, and the iOS delegate methods are in the documentation for reference.

src/video/uikit/SDL_uikitevents.m

@@ -71,12 +71,12 @@ static BOOL UIKit_EventPumpEnabled = YES;
 
 - (void)applicationDidBecomeActive
 {
-    SDL_OnApplicationDidBecomeActive();
+    SDL_OnApplicationDidEnterForeground();
 }
 
 - (void)applicationWillResignActive
 {
-    SDL_OnApplicationWillResignActive();
+    SDL_OnApplicationWillEnterBackground();
 }
 
 - (void)applicationDidEnterBackground