Don't eat TAB unconditionally in wxComboCtrl

This prevented TAB navigation from doing anything at all when the focus
was on wxComboCtrl in wxGTK and, probably, all the other non-MSW ports
(in wxMSW TAB navigation happens before normal key processing, so this
check was irrelevant there).

src/common/combocmn.cpp

@@ -751,9 +751,7 @@ void wxComboBoxExtraInputHandler::OnKey(wxKeyEvent& event)
 
     if ( !combo->GetEventHandler()->ProcessEvent(redirectedEvent) )
     {
-        // Don't let TAB through to the text ctrl - looks ugly
+        event.Skip();
-        if ( event.GetKeyCode() != WXK_TAB )
-            event.Skip();
     }
 }