git-format-patch --in-reply-to: accept <message@id> with angle brackets

git-format-patch --in-reply-to: accept <message@id> with angle brackets

This will allow RFC-literate users to say:

	format-patch --in-reply-to='<message.id@site.name>'

without forcing them to strip the surrounding angle brackets
like this:

	format-patch --in-reply-to='message.id@site.name'

We accept both forms, and the latter gets necessary < and >
around it as before.

Signed-off-by: Junio C Hamano <gitster@pobox.com>