Allow using wxCompositeWindow<T> as wxDataViewCtrl inline editor.

Allow using wxCompositeWindow<T> as wxDataViewCtrl inline editor.

wxDVC inline editing code attaches some event handlers to the editor
control; most importantly, it watches for Enter key and for focus
changes. If the editor control is a composite window, these events occur
in a sub control and never reach wxDVC code.

Fix this by forwarding events to the main window of the composite
control. Only events required by wxDVC are implemented for now.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69470 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775