[Xcb] util/image doxygen in; x11perf does arcs

[Barton C Massey]

I finished porting x11perf/do_arcs.c .  I wish someone would
port the rest of these for me. It's actually kind of
relaxing and fun, but it took me about 1.5 hours for about
1000 lines of code, so some parallel work would be great.

I also updated the doxygen comments for my new util/image
library.  The doxygen still needs some love, I think, but
it's at least as good as it ever was, and matches the new
functionality.

  git://people.freedesktop.org/~bart/git/x11perf.git
  git://people.freedesktop.org/~bart/git/util.git

    Bart Massey
    bart at cs.pdx.edu