user/gtk+2.0: overhaul (see commit msg)

* Insert static -lintl from gettext-tiny into build.  This makes the GTK
  LOCALEDIR finally /usr/share/locale instead of /usr/lib/locale.

* Remove old replaces= from Alpine.  This isn't Alpine, we never had a gtk+.

* Shuffle variables around to match Adélie preferred style.

* Don't define a global `subpkg` variable for a single subpackage(???)

* Modernise.

* Take maintainership over.