Also, fix the same core dump in the case where there are no `_build' lines.
These should probably both emit a warning, so the user knows what happened.
It require "_crunch" section in /etc/man.conf to re-compress the compressed man pages.
It handle symbolic links, but at this time no hard links.
config files are stolen from man with few changes to support "_crunch" section.
catman.8 miss the "full moon" joke, I can't remember it, if you can pleas add it :-)