Still run all the tests by default but allow specifying --dc or --gc as well
as --paint, --client or --memory to test just the specified kinds of DCs.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73470 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775