Motivation for this change

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.

It could be possible to use the --enable-gpg-is-gpg2 configure flag to keep the old binary names, but in the long run I think everyone should converge to the new naming. We could use this while waiting for the 2.2 release but this would only postpone the work.

It could however be reasonable to use the --enable-gpg-is-gpg2 until the 17.09 branch of, and then have a 6 month window to be sure this renaming does not cause issue for next stable release.

I am of course open to discussions on this subject.

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

Things done

Please check what applies. Note that these are not hard requirements but merely serve as information for reviewers.

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.