implement wxEventLoop::DispatchTimeout() for wxGTK (thanks Paul) and rewrote it to not use wxEventLoopImpl which it doesn't need

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57581 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/evtloop.h

@@ -126,6 +126,8 @@ protected:
     #include "wx/osx/evtloop.h"
 #elif defined(__WXDFB__)
     #include "wx/dfb/evtloop.h"
+#elif defined(__WXGTK20__)
+    #include "wx/gtk/evtloop.h"
 #else // other platform
 
 #include "wx/stopwatch.h"   // for wxMilliClock_t