can be overridden in wxTLW to set WM hints.
Actually did that for wxGTK, nothing required for
wxMSW, no idea about wxMac.
Documented this in tlw.tex.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42718 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775