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/tools/security/gnupg/gpgkey2ssh-20.patch

@@ -7,7 +7,7 @@ index 903fb5b..d5611dc 100644
  
    ret = asprintf (&command,
 -		  "gpg --list-keys --with-colons --with-key-data '%s'",
-+		  "@out@/bin/gpg2 --list-keys --with-colons --with-key-data '%s'",
++		  "@out@/bin/gpg --list-keys --with-colons --with-key-data '%s'",
  		  keyid);
    assert (ret > 0);