We need some hacks for the older systems before including this header, extract
them from src/x11/utilsx.cpp into a new private header to be able to reuse it
from wxGTK in the next commit.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71372 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
