Update gtksourceview3 to 3.22.2.
Record missing depends.
-ref: drop $MCom$ tag.
-ref: mention correct port in pkg-descr where the docs come from.
Obtained from: gnome devel repo
Add gtksourceview 3.4.2.
GtkSourceView is a text widget for Gtk+-3 that provides syntax highlighting
and other features typically expected in a source code editor.
Obtained from: gnome team repo