solved color depth issues on osx

platform/osx/os_osx.mm

@@ -903,7 +903,7 @@ void OS_OSX::initialize(const VideoMode& p_desired,int p_video_driver,int p_audi
 	unsigned int attributeCount = 0;
 
 	// OS X needs non-zero color size, so set resonable values
-	int colorBits = 24;
+	int colorBits = 32;
 
 	// Fail if a robustness strategy was requested