[Aide] GPG checking support scripts

[Richard van den Berg]

Vincent Danen wrote:
> Anyways, these are the scripts that will be shipping in the Annvix aide
> package (they may evolve a bit yet as I keep fiddling, but I think
> they're basically complete for the most part right now).

Since they serve a different purpose, I've added them to the AIDE
contrib directory as gpg2_check.sh and gpg2_update.sh. Thanks for the
contribution.

Sincerely,

Richard van den Berg