Merge branch 'uk/signature-is-good-after-key-expires'

A signature on a commit that was GPG signed long time ago ought to
be still valid after the key that was used to sign it has expired,
but we showed them in alarming red.

* uk/signature-is-good-after-key-expires:
  gpg-interface: signatures by expired keys are fine

diff --cc gpg-interface.c
Simple merge