Small fix to "correctly" parse PGP inline signed mails by
(presumingly) GPGMail 1.4.1

Content-Type: application/pgp; format=text; x-action=sign

and inline separators as:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

<body>
-----BEGIN PGP SIGNATURE-----

<signature>
-----END PGP SIGNATURE-----

former version only tried to decrypt body, which in this case obviously
fails.
cleanup: previous patch
Multiple Signers did not work with gpgme 2.0.2

Exchanged :signers with :signer, this seems to allow to create a
signature based on account or from.

Previously always the default or first private key had been used.

But I haven't communicated with the developers of gpgme.

Signed-off-by: Gaute Hope <eg@gaute.vetsj.com>