Idea for turbo expiry

[Jason L Tibbitts III <tibbs@hpc.uh.edu>]

I dipped into the expiry code to see why it was taking so much CPU every
time I exited an nnml group.  It looks to me like it builds a list of all
expirable articles and stats each of them in turn to see if they're old
enough.

My idea is to make the assumption that articles come in chronologically, so
that if an article has a lower number, it it older.  Thus you can run the
list of articles in numerical order and bail after you find one that is too
young to expire.  I figure (judging from how much mail I save in some of my
active folders) that this would cut my expiry time by a factor of 100 or
more.

Yes, it's easy to fool.  Just touch (or edit) a random article and watch it
hold up expiry of everything after it.  I'm willing to make that sacrifice,
at least for some groups.

 - J<