Hmm. Telling xvfb to default to a TrueColor visual did help, in that

Hmm. Telling xvfb to default to a TrueColor visual did help, in that
it got rid of the bogus backgrounds on all the text; but on the
other hand it mysteriously caused all the images to become black and
white! Serves me right for testing with Bridges which was B&W to
start with. Instead, we'll just tell xvfb to use a 24-bit display
and let it sort out the visuals for itself; that seems to work better.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@7932 cda61777-01e9-0310-a592-d414129be87e