Bug#3276: screen upgrade trashes running sessions...

[eichin@kitten.gen.ma.us (Mark W. Eichin)]

> Also, what is this about checking the permissions? who's permissions?

The permissions on /tmp/screens that this rm -rf is intended to fix.
(What brought it to my attention is that I went from 3.7.1-3 to -4,
which clearly *didn't* have anything wrong with /tmp/screens, but it
nuked it anyway.) I'd be happy with that check -- if anyone is still
running a version that does have the permission problem, there isn't
much we can do to save them, I suppose (since a chown/chmod won't
really be "safe".)