adding errc to support sed (FreeBSD)

["writeonce@midipix.org" <writeonce@midipix.org>]

Greetings,

The FreeBSD implementation of sed uses errc; its implementation should 
probably be as simple as:

_Noreturn void errc(int eval, int status, const char *fmt, ...)
{
         va_list ap;
         va_start(ap, fmt);
         vwarnx(status, fmt, ap);
         va_end(ap);
         exit(eval);
}

The FreeBSD sed also needs a couple of macros that are currently not 
defined, specifically ALLPERMS, DEFFILEMODE and REG_STARTEND.  Any 
reason not to add them when _BSD_SOURCE is defined?

Kind regards,
zg