wxListBox::GetSelection returning -1 now doesn't assert; wxProp improvements
for wxGTK; parser.y includes <io.h> under VC++ to eliminate 'read' warning
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@709 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775