main() is now always in the program. Also added a
macro that doesn't set main at all so that users
can have their own.
The isosurf sample doesn't work anymore.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6459 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
