wxMutexGuiLocker and wxThread_IsMain to assist with dealing with GUI
access from non-GUI threads.
wxPyOnDemandOutputWindow is now thread safe if non-GUI threads use
print, sys.stdout.write, etc.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@9590 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
