Fix up some retain/release issues with UIScreenMode objects.

Fixes Bugzilla #1191.

This patch is based on work done by Vittorio Giovara.

src/video/uikit/SDL_uikitvideo.m

@@ -212,7 +212,8 @@ UIKit_AddDisplay(UIScreen *uiscreen, UIScreenMode *uimode, int w, int h)
     mode.h = h;
     mode.refresh_rate = 0;
     
-    [uimode retain];
+    [uimode retain];  // once for the desktop_mode
+    [uimode retain];  // once for the current_mode
     mode.driverdata = uimode;
 
     SDL_zero(display);
@@ -286,13 +287,14 @@ UIKit_VideoQuit(_THIS)
         UIScreen *uiscreen = (UIScreen *) display->driverdata;
         [uiscreen release];
         display->driverdata = NULL;
+        [((UIScreenMode *) display->desktop_mode.driverdata) release];
+        display->desktop_mode.driverdata = NULL;
+        [((UIScreenMode *) display->current_mode.driverdata) release];
+        display->current_mode.driverdata = NULL;
         for (j = 0; j < display->num_display_modes; j++) {
             SDL_DisplayMode *mode = &display->display_modes[j];
-            UIScreenMode *uimode = (UIScreenMode *) mode->driverdata;
-            if (uimode) {
-                [uimode release];
-                mode->driverdata = NULL;
-            }
+            [((UIScreenMode *) mode->driverdata) release];
+            mode->driverdata = NULL;
         }
     }
 }

src/video/uikit/SDL_uikitwindow.m

@@ -151,8 +151,13 @@ UIKit_CreateWindow(_THIS, SDL_Window *window)
             if (bestmode) {
                 UIScreenMode *uimode = (UIScreenMode *) bestmode->driverdata;
                 [uiscreen setCurrentMode:uimode];
-                display->desktop_mode = *bestmode;
+
+                // desktop_mode doesn't change here (the higher level will
+                //  use it to set all the screens back to their defaults
+                //  upon window destruction, SDL_Quit(), etc.
+                [((UIScreenMode *) display->current_mode.driverdata) release];
                 display->current_mode = *bestmode;
+                [((UIScreenMode *) display->current_mode.driverdata) retain];
             }
         }
     }