add MutexGuiEnter/Leave to wxAppTraits, integrate native GTK+ GUI locking

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@50757 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/threadpsx.cpp

@@ -1800,12 +1800,12 @@ static void DeleteThread(wxThread *This)
     }
 }
 
-void wxMutexGuiEnter()
+void wxMutexGuiEnterImpl()
 {
     gs_mutexGui->Lock();
 }
 
-void wxMutexGuiLeave()
+void wxMutexGuiLeaveImpl()
 {
     gs_mutexGui->Unlock();
 }