Fix Mac build, was broken at da66806...

... Fix I wrote as a late 2.3.2 pull request was before I did other cuts and
pastes for cycle breaking.  Replicating the patch in the new place without
extra #include directives did not compile.

src/KeyboardCapture.cpp

@@ -17,7 +17,9 @@
 #include <gtk/gtk.h>
 #endif
 
+#include <wx/button.h>
 #include <wx/eventfilter.h>
+#include <wx/toplevel.h>
 #include <wx/weakref.h>
 #include <wx/window.h>