gnupg: Add gnupg 2.1 as default

Additionally, move all gnupg expressions into the gnupg folder.

pkgs/tools/security/gnupg/1compat.nix

@@ -0,0 +1,20 @@
+{ stdenv, gnupg, coreutils, writeScript }:
+
+stdenv.mkDerivation {
+  name = "gnupg1compat-0";
+
+  builder = writeScript "gnupg1compat-builder" ''
+    # First symlink all top-level dirs
+    ${coreutils}/bin/mkdir -p $out
+    ${coreutils}/bin/ln -s ${gnupg}/* $out
+
+    # Replace bin with directory and symlink it contents
+    ${coreutils}/bin/rm $out/bin
+    ${coreutils}/bin/mkdir -p $out/bin
+    ${coreutils}/bin/ln -s ${gnupg}/bin/* $out/bin
+
+    # Add gpg->gpg2 and gpgv->gpgv2 symlinks
+    ${coreutils}/bin/ln -s gpg2 $out/bin/gpg
+    ${coreutils}/bin/ln -s gpgv2 $out/bin/gpgv
+  '';
+}