games/angband: update to 4.2.2, latest upstream

The release notes are at
https://github.com/angband/angband/releases/tag/4.2.2

Angband looks like it's in the process or a project-reorganization.
Sources have moved to github; the official site is being changes
as well. Docs have gone to sphinx, and build looks like it's moving
to CMake -- but incomplete.

This update pulls in the changes to distribution and build so far:

• MASTER_SITES is set explicitly; upstream rolls a release tarball, and I don't want to grab the GH auto-rolled one.
• ncurses needs some linker-flag-magic because it's linked into an intermediate static library.
• The manual is now built with sphinx. Upstream wants the "better" sphinx theme, but that isn't packaged; I picked a different one at random. Since the generated HTML is installed without its supporting stylesheets or javascript, the difference is unimportant.

Play-tested in text (ncurses) and X11 modes, at least to the point
that I enter the dungeon and get eaten by a grue.