a new GNATS report, and a new script

[Mark Linimon]

As documented on http://people.freebsd.org/~linimon/studies/prs, I have
added a page that gathers together the well-known PRs that we keep seeing:

  http://people.freebsd.org/~linimon/studies/prs/well_known_prs.html

This is driven off of a file ~linimon/public_html/wellknown.prs, which
includes both commentary and a list of PR numbers.  (The commentary is
simply copied to the HTML file; any line containing only numerics is
magically processed as a PR number).

I am hoping that this will be a way for us to do some data-reduction,
rather than trying to cross-index PRs.  Please feel free to suggest
more entries for wellknown.prs!

Thanks to pgollucci for the Perl help.

Also, per suggestion from keramida, I've added a script to freefall
that picks a random PR and displays it:

 ~gnats/tools/show-random-pr      show a random PR for <tag> and <category>

A companion script, show-random-unassigned-pr, will pick only ones for
freebsd-bugs.  (Note that show-random-pr patch docs will return no
results; it needs work to understand that 'unassigned' is not merely
'freebsd-bugs').

mcl