Mark event loop nesting more carefully.

Fixes #5506. I hope fixes #5508.

Telegram/SourceFiles/platform/platform_specific.h

@@ -35,6 +35,8 @@ PermissionStatus GetPermissionStatus(PermissionType type);
 void RequestPermission(PermissionType type, Fn<void(PermissionStatus)> resultCallback);
 void OpenSystemSettingsForPermission(PermissionType type);
 
+bool NativeEventNestsLoop(void *message);
+
 QString SystemLanguage();
 QString SystemCountry();