* pgg-gpg.el (pgg-gpg-verify-region): Filter out stuff into output

* pgg-gpg.el (pgg-gpg-verify-region): Filter out stuff into output
buffer and error buffer depending on type of information.

* mml2015.el (mml2015-gpg-extract-signature-details): Parse
--status-fd stuff even if gpg.el is not used (revert earlier
change).
(mml2015-pgg-{clear-,}verify): Store both output and errors as
gnus details.
(mml2015-pgg-{clear-,}verify): Extract signature info from errors
buffer.