[Nmh-workers] More autoconf poo: BSD42

[Ken Hornstein]

So, I am cleaning up more autoconf cruft, and one remaining thing
is the OS-specific defines.  I don't think anyone will object to
the removal of SCO_5_STDIO specific code, but there is one that is
used a surprising amount: BSD42.

This code has two purposes: if you have a & in the GECOS field, it
substitutes in your login name in to your real name field.  Personally I
always found this feature a bit dubious, and from my experience not much
supports that.  I propose we just junk this support.

The other use of BSD42 seems to be in msh.c; basically, if we get
interrupted in a signal, longjmp() out of the signal handler back
to the main command loop.  I guess this code was before signals
interrupted system calls?  Anyway, I am thinking that this can be
junked as well.  Any objections?

(Okay, for purists; BSD42 also controls the use of the MIME content
cache, for reasons I do not pretend to understand).

--Ken