1. -e mode to expunge a port via pkg_delete, and optionally
remove its distfiles
2. -s and -e modes now respect -b (backup) and -d|D options
regarding always deleting (or not deleting) distfiles
1. Re-factor more code out into functions, and move them earlier in the
script so that they are available to the new features.
2. Clean up the code in a few places to make it slightly more efficient,
and a lot more readable.
1. Fix exit status of various code paths to be more in keeping
with Unix tradition 
2. Be a lot more thorough about killing off errant children when
the user hits ^C 
3. If the directory referred to by PKGREPOSITORY exists, use it
to store packages built for -b and -g instead of HOME 
My thanks to both Darren and James for their patience and testing
of several development versions to nail down bugs 2 and 3.
Brought to my attention by: Darren Pilgrim <email@example.com> 
Brought to my attention by: James O'Gorman <firstname.lastname@example.org>