[PATCH] mailinfo: reset CTE after each multipart

If the first part uses quoted-printable to protect iso8859-1
name in the commit log, and the second part was plain ascii text
patchfile without even Content-Transfer-Encoding subheader, we
incorrectly tried to decode the patch as quoted printable.

Signed-off-by: Junio C Hamano <junkio@cox.net>