[Nmh-workers] signed/unsigned cleanup & m_getfld()

[Ken Hornstein]

Okay, so I've started to clean up the whole signed/unsigned mess ... and
I realize that m_getfld() is now the largest source of warnings.
Specifically, m_getfld() takes as arguments 2 and 3 unsigned char *.

This is not new; it's always been that way.  I gather that back in
the day nobody really cared, as matchc() (used by m_getfld()) returned
unsigned char *, but took char * as arguments.  Well, it wasn't even
prototyped in mh-6.8.5, so perhaps that's why no one really noticed.
But regardless, a cleanup is long overdue.

Now m_getfld() is really David's baby, so I'm reluctant to mess with it.
David, I'll leave it up to you; if you want to change the prototype for
m_getfld() to take char *, that's fine with me.  If you want to leave it
so we need explicit casts everywhere m_getfld() is called, that's also
fine with me; I'll put those in.

(If I was voting, I will confess that I think the prototype of m_getfld()
should be changed, but like I said, it's totally your call).

--Ken