gpg: Use just the addrspec from the Signer's UID.

gpg: Use just the addrspec from the Signer's UID.

* g10/parse-packet.c (parse_signature): Take only the addrspec from a
Signer's UID subpacket.
--

This is to address a problem in the currentr OpenKeychain which put
the entire UID into the subpacket.  For example our Tofu code can only
use the addrspec and not the entire UID.

Reported-by: Wiktor Kwapisiewicz <wiktor@metacode.biz>
Signed-off-by: Werner Koch <wk@gnupg.org>
(cherry picked from commit 05204b72497db093f5d2da4a2446c0264a946296)

Gbp-Pq: Topic from-2.2.16
Gbp-Pq: Name gpg-Use-just-the-addrspec-from-the-Signer-s-UID.patch