gnupg: 2.1.22 -> 2.1.23

This release in a RC for gnupg-2.2. The main difference as far as
nixpkgs is concerned is that the binary `gpg2` is now called `gpg` and
`gpgv2` is called `gpgv`.

This update fixed all explicit use of `gpg2` and `gpgv2` across nixpkgs,
but there might be some packaged software that internally use `gpg2`
not handeled by this commit.

See http://lists.gnu.org/archive/html/info-gnu/2017-08/msg00001.html
for full release information

pkgs/development/ruby-modules/gem-config/default.nix

@@ -242,7 +242,7 @@ in
 
       substituteInPlace lib/sup/crypto.rb \
         --replace 'which gpg2' \
-                  '${which}/bin/which gpg2'
+                  '${which}/bin/which gpg'
     '';
   };