Replace wxEVT_GRID_HIDE_EDITOR usage with CallAfter

This simplifies the code by removing the need for a special event,
and also means the combox popup handler is no longer needed to reset
the inSetFocus flag for the closing handler.

include/wx/generic/grideditors.h

@@ -27,6 +27,8 @@ public:
     {
     }
 
+    void DismissEditor();
+
     void OnKillFocus(wxFocusEvent& event);
     void OnKeyDown(wxKeyEvent& event);
     void OnChar(wxKeyEvent& event);
@@ -335,8 +337,7 @@ public:
 protected:
     wxComboBox *Combo() const { return (wxComboBox *)m_control; }
 
-    void onComboCloseUp(wxCommandEvent& evt);
-    void onComboDropDown(wxCommandEvent& evt);
+    void OnComboCloseUp(wxCommandEvent& evt);
 
     wxString        m_value;
     wxArrayString   m_choices;