Allow in body headers beyond the in body header prefix.

Allow in body headers beyond the in body header prefix.

- handle_from is fixed to not mangle it's input line.

- Then handle_inbody_header is allowed to look in
  the body of a commit message for additional headers
  that we haven't already seen.

This allows patches with all of the right information in
unfortunate places to be imported.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>