Fix spelling in comments and documentation using codespell

Apply the utility from https://github.com/codespell-project/codespell/
to fix spelling issues in the headers under both include and interface
directories and add a file with a couple of exceptions.

The exact command line used was:

    $ codespell -w -I misc/scripts/codespell.ignore -i 3 in*

include/wx/odcombo.h

@@ -369,7 +369,7 @@ protected:
     // NULL popup can be used to indicate default interface
     virtual void DoSetPopupControl(wxComboPopup* popup) wxOVERRIDE;
 
-    // clears all allocated client datas
+    // clears all allocated client data
     void ClearClientDatas();
 
     wxVListBoxComboPopup* GetVListBoxComboPopup() const