(remove global function to handle destroyed signal)
This is needed for applications because the global function is not exported, yet it
is used by the opengl library. An alternative is to add utils.cpp to the opengl library
Thanks @seandepagnier
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78384 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775