Cleaning out obsolete bugs in bugzilla

Another part of bugzilla spring cleaning (though obviously it's an
ongoing task) I'd like to do is establish a process for closing (in
some form) bugs old enough that the likelihood they will ever get
fixed is within epsilon of zero.  And maybe even closing several of
them.  But as along we we can establish a process for efficiently
closing them (i.e., avoiding drawn out discussions on whether they
should have been closed, and the manor in which they were closed),
then I think we can make better progress at clearing them out (or at
least I know I could ... :-)).

An example of the kind of bug I'm thinking of is this one:
https://sourceware.org/bugzilla/show_bug.cgi?id=8769
gdb 6.1 doesn't build on hpux.

I don't have a strong opinion on what flavor of RESOLVED to close
these as, but I do have a strong opinion that we should close them.  I
can't see any sufficiently significant value to warrant keeping them.

Another bug tracking system I've used has the choice of "Obsolete".
Bugzilla doesn't have it by default but I have confirmed that we can add it.
OTOH, using WONTFIX is fine by me too.  Or we could pick something else.
I'm mentioning the existence of the ability to use something other
than WONTFIX in case people have a strong opinion on not using
WONTFIX.

Comments?