Merge pull request #2392 from tbodt/mac-panels-fix

UI: Add missing function delcaration

UI/platform.hpp

@@ -65,4 +65,5 @@ RunOnceMutex GetRunOnceMutex(bool &already_running);
 #ifdef __APPLE__
 void EnableOSXVSync(bool enable);
 void EnableOSXDockIcon(bool enable);
+void InstallNSApplicationSubclass();
 #endif