[gmime-devel] improve crypto handling

[Daniel Kahn Gillmor <dkg fifthhorseman net>]

Attached are a series of patches to improve gmime's handling of
encrypted messages.  There's nothing particularly radical here, but it
makes the test suite work against the "modern" GnuPG suite (2.1.x), it
makes the test suite actually run crypto tests when invoked from the
tarball, and it supports extraction of session keys upon request, at
least for OpenPGP-encrypted mail.

You can also pull these patches directly from the crypto-improvements
branch at https://gitlab.com/dkg/gmime if that makes it easier to
merge.