telnet:
- will apparently sometimes assert in ungetch. I think I've
fixed this, so if you still see it let me know.
- hangs if you telnet to chargen port and push ^Z
(due to bogus protocol negotiation attempts)
- binary mode doesn't handle crlf right
- should warn if the connection isn't encrypted

telnetd:
- hangs if you do the following:
telnet
log in
cat >/dev/null
type 256 'a's with no CRs
*THIS IS A KERNEL BUG* Patch enclosed.

- crashes in ncurses if the terminal type is undefined,
with some versions of ncurses.
- should allow passing random user envs as "TELNET_*"
- should set REMOTEHOST to the remote hostname
- passes login the -p flag instead of sending envs explicitly
- should only use included logout() et al. if real ones aren't
available in system libs.
- addarg() in sys_term.c does some very questionable casts.