Update the code for the iOS demos to handle modern devices. Fixes bug #3337

Xcode-iOS/Demos/src/common.h

@@ -4,14 +4,7 @@
  *  use however you want
  */
 
-#if __TVOS__
-#define SCREEN_WIDTH 1920
-#define SCREEN_HEIGHT 1080
-#else
-#define SCREEN_WIDTH 320
-#define SCREEN_HEIGHT 480
-#endif
-
 extern int randomInt(int min, int max);
 extern float randomFloat(float min, float max);
 extern void fatalError(const char *string);
+extern double updateDeltaTime();