asciidoc: add missing dependencies

Make asciidoc full featured by adding dependencies and fixing up impurities. See commit messages for details.

This increases the closure size from 255 MiB to 1.5 GiB. A few packages use asciidoc for generating documentation:

$ git grep -l asciidoc
pkgs/applications/version-management/git-and-tools/cgit/default.nix
pkgs/applications/version-management/git-and-tools/default.nix
pkgs/applications/version-management/git-and-tools/git-bz/default.nix
pkgs/applications/version-management/git-and-tools/git/default.nix
pkgs/applications/version-management/git-and-tools/tig/default.nix
pkgs/applications/window-managers/awesome/default.nix
pkgs/development/tools/build-managers/ninja/default.nix
pkgs/games/wesnoth/default.nix
pkgs/os-specific/linux/kernel/perf.nix
pkgs/tools/filesystems/httpfs/default.nix
pkgs/tools/text/unoconv/default.nix
pkgs/tools/typesetting/asciidoc/default.nix
pkgs/top-level/all-packages.nix
pkgs/top-level/release-python.nix

The build-time storage footprint will increase for those. But the asciidoc hash shouldn't be retained, so the extra storage can be garbage collected afterwards. And binary channel users shouldn't notice any difference at all (nothing extra to download).

We can of course add asciidocLight/Full attributes, but I remember having to do a workaround in the ninja expression to make it work with the current (incomplete) asciidoc expression, so having a full featured asciidoc tool may be easier for us.

If you want minimal, you can always pass enableStandardFeatures = false to the asciidoc expression.