Removed msgchk(1) as it is hardly useful without POP support.

Removed msgchk(1) as it is hardly useful without POP support.
It is questionable if msgchk(1) provides more information than:
	ls -l /var/mail/meillo
It does separate between old and new mail, but that's not very useful
and can be found out with stat(1) too. A very small shell script should
be equally useful, if there's someone who really uses msgchk(1) and not
simply `inc's.
Concerning the administrative uses of msgchk(1), i.e. querying a set of
users, that's no MUA's task and thus a reason to remove the tool. But
eventually, the question remains the same: What does it provide more than
`ls -l' and `ls -lu'? Is it worth to keep it around? IMO, no.