Move photo ID display code from epg.el to gnus/mml2015.el.

Move photo ID display code from epg.el to gnus/mml2015.el.

2012-12-26  Daiki Ueno  <ueno@gnu.org>
* mml2015.el (mml2015-epg-signature-to-string): New function.
(mml2015-epg-verify-result-to-string): New function.
(mml2015-epg-decrypt, mml2015-epg-clear-decrypt, mml2015-epg-verify)
(mml2015-epg-clear-verify): Use mml2015-epg-verify-result-to-string
instead of epg-verify-result-to-string.
(epg-signature-key-id, epg-signature-to-string): Autoload.
(epg-verify-result-to-string): Remove autoload.

2012-12-25  Adam Sjøgren  <asjo@koldfront.dk>
* mml2015.el (mml2015-epg-key-image): New function, to retrieve photo
ID image from GPG public key.
(mml2015-epg-key-image-to-string): New function.