darcs patch: add test that X11 will actually build.

Just for future benefits, it seems a good idea to occasionally check that the X11 library actually can be built. This patch is untested, since the X11 library won't build for me. David Wed May 16 09:26:26 PDT 2007 David Roundy <droundy@darcs.net> * add test that X11 will actually build.