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/applications/misc/gpg-mdp/default.nix

@@ -19,11 +19,11 @@ in stdenv.mkDerivation {
       --replace "alias echo=/bin/echo" ""
 
     substituteInPlace ./src/config.c \
-      --replace "/usr/bin/gpg" "${gnupg}/bin/gpg2" \
+      --replace "/usr/bin/gpg" "${gnupg}/bin/gpg" \
       --replace "/usr/bin/vi" "vi"
 
     substituteInPlace ./mdp.1 \
-      --replace "/usr/bin/gpg" "${gnupg}/bin/gpg2"
+      --replace "/usr/bin/gpg" "${gnupg}/bin/gpg"
   '';
   # we add symlinks to the binary and man page with the name 'gpg-mdp', in case
   # the completely unrelated program also named 'mdp' is already installed.