#5610: use \Z not $ so we don't eat extra chars when body part ends with \r\n.

#5610: use \Z not $ so we don't eat extra chars when body part ends with \r\n.

If a body part ended with \r\n, feedparser, using '$' to terminate its
search for the newline, would match on the \r\n, and think that it needed
to strip two characters in order to account for the line end before the
boundary.  That made it chop one too many characters off the end of
the body part.  Using \Z makes the match correct.

Patch and test by Tony Nelson.