Copypaste SDL_NSLog to UIKit backend, document it as such

src/SDL_log.c

@@ -400,8 +400,8 @@ SDL_LogOutput(void *userdata, int category, SDL_LogPriority priority,
         SDL_snprintf(tag, SDL_arraysize(tag), "SDL/%s", GetCategoryPrefix(category));
         __android_log_write(SDL_android_priority[priority], tag, message);
     }
-#elif defined(__APPLE__) && defined(SDL_VIDEO_DRIVER_COCOA)
-    /* Technically we don't need SDL_VIDEO_DRIVER_COCOA, but that's where this function is defined for now.
+#elif defined(__APPLE__) && (defined(SDL_VIDEO_DRIVER_COCOA) || defined(SDL_VIDEO_DRIVER_UIKIT))
+    /* Technically we don't need Cocoa/UIKit, but that's where this function is defined for now.
     */
     extern void SDL_NSLog(const char *text);
     {

src/video/cocoa/SDL_cocoavideo.m

@@ -252,6 +252,9 @@
  *
  * This doesn't really have aything to do with the interfaces of the SDL video
  *  subsystem, but we need to stuff this into an Objective-C source code file.
+ *
+ * NOTE: This is copypasted in src/video/uikit/SDL_uikitvideo.m! Be sure both
+ *  versions remain identical!
  */
 
 void SDL_NSLog(const char *text)

src/video/uikit/SDL_uikitvideo.m

@@ -247,12 +247,18 @@ static void UIKit_DeleteDevice(SDL_VideoDevice * device)
  *
  * This doesn't really have aything to do with the interfaces of the SDL video
  *  subsystem, but we need to stuff this into an Objective-C source code file.
+ *
+ * NOTE: This is copypasted from src/video/cocoa/SDL_cocoavideo.m! Thus, if
+ *  Cocoa is supported, we use that one instead. Be sure both versions remain
+ *  identical!
  */
 
+#if !defined(SDL_VIDEO_DRIVER_COCOA)
 void SDL_NSLog(const char *text)
 {
     NSLog(@"%s", text);
 }
+#endif /* SDL_VIDEO_DRIVER_COCOA */
 
 /*
  * iOS Tablet detection