Enabling the use of masks for wxGTK in some of the demos

Enabling the use of masks for wxGTK in some of the demos

wxWindow.GetHandle returns the X-Window instead of the GtkWidget
pointer so the X-Window can be given to other Python modules such as
VTK.

wxPython.lib.vtk updated to get the window handle at widget creation
instead of in the constructor.

other updates

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@5147 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775