Move definition of wxMenuItem to /gtk/menuitem.h
Radical change of how to insert a child into a
paren window. As C++ doesn't have any VMT in
a class's consructor, I have to use a callback.
Fixed culumn resizing bug in wxListCtrl
Fixed menu height bug in MDI code
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775