git-send-email: do not double-escape quotes from mutt

git-send-email: do not double-escape quotes from mutt

mutt saves aliases with escaped quotes in the form of:

	alias dot \"Dot U. Sir\" <somebody@example.org>

When we pass through our sanitize_address routine,
we end up with double-escaping:

	 To: "\\\"Dot U. Sir\\\" <somebody@example.org>

Remove the escaping in mutt only for now, as I am not sure
if other mailers can do this or if this is better fixed in
sanitize_address.

Cc: Remi Lespinet <remi.lespinet@ensimag.grenoble-inp.fr>
Cc: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>