fully initialize GTypeInfo structure

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75168 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
use gtk_combo_box_get_wrap_width(), we require GTK+ 2.6 now

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75169 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775