* Makefile.am (EXTRA_DIST): dist cleanup-man-pages.sh so it's in
the tarball if packagers want to run it
* cleanup-man-pages.sh: Add a script which munges all the internal
API man pages out of the Doxygen output. This reduces the size of
the installed man pages from 7 to 2 megs, and avoids
namespace-polluting pages. Right now (like Doxygen) this script
isn't in the build, it's something packagers can do manually.