[9fans] p9p factotum available for plan 9

[erik quanstrom <quanstro@quanstro.net>]

	contrib/install quanstro/nfactotum

thanks to a bunch of work by brian stuart and Coraid
paying both of us to work on these things, we've gotten
together a plan 9 version of p9p's factotum. the main
purpose of doing this is to support dsa and rsa verify
and sign.  of course the huge side benefit is that it's much
easier to add protocols to factotum.

i am currently running nfactotum as the factotum in
my terminal kernel, and i've been testing (but not
depending on) a cpu kernel with nfactotum built in.
it's verified that cpu, ssh 1 (client), telnet (client) work.

imap/smtpd passwd and cram and are untested.
i'm unsure if i've tested ssh server.  p9cr is missing some bits
to make vnc work.

telnet (server) is known broken.  i don't think it's a hard fix.
however, the diagnostic is fortune-worthy:

!factotum protocol botch 0 ok bad authentication failed

- erik