notmuch-show --verify will now also process S/MIME multiparts if
encountered. Requires gmime-2.6 and gpgsm.
Based on work by Jameson Graef Rollins <jrollins@finestructure.net>.
The test is pretty much cut and paste from the PGP/MIME version, with
obvious updates taken from notmuch output. This also requires setting
up gpgsm infrastucture.
Test the ability of notmuch-mua-mail to send S/MIME signed (and
encrypted) messages; this really relies on existing functionality in
message-mode.
The generated keys and messages will later be useful for testing the
notmuch CLI.
