egg-list-box: Add gobject-introspection support.

Also build it as a shared library.
egg-list-box: make egg_list_box_set_sort_func() usable from gjs

Use a function signature with explicit pointer types and annotate egg_list_box_set_sort_func
properly.
Split 'egg-list-box/' into commit 'd82ea50f8657fdf484d8965330b8f4f29f6db8a2'

git-subtree-dir: egg-list-box
git-subtree-mainline: 76ed5b9503326ee9b8e8cc94d6f7fa24d33c1878
git-subtree-split: d82ea50f8657fdf484d8965330b8f4f29f6db8a2