Call gtk_window_set_keep_above() to force the message dialog to be above the other windows (some WMs do this by default anyhow but not all). Closes #11163. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61828 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775