Cocoa: don't fail outright if we see an unknown display format.

Just treat it as ARGB8888.

src/video/cocoa/SDL_cocoamodes.m

@@ -192,9 +192,16 @@ GetDisplayMode(_THIS, const void *moderef, CVDisplayLinkRef link, SDL_DisplayMod
         mode->format = SDL_PIXELFORMAT_ARGB8888;
         break;
     case 8: /* We don't support palettized modes now */
-    default: /* Totally unrecognizable bit depth. */
         SDL_free(data);
         return SDL_FALSE;
+    default:
+        /* Totally unrecognizable format. Maybe a new string reported by
+           CGDisplayModeCopyPixelEncoding() in a future platform SDK.
+           Just lie and call it 32-bit ARGB for now, so existing programs
+           don't completely fail on new setups. (most apps don't care about
+           the actual mode format anyhow.) */
+        mode->format = SDL_PIXELFORMAT_ARGB8888;
+        break;
     }
     mode->w = width;
     mode->h = height;