docs: RygelMediaEngine: Mention C types.
docs: RygelMediaEngine: Mention C types.

Tarnyko/rygel,Pelagicore/Media-Manager-Rygel-patched,GNOME/rygel,jku/rygel,Tarnyko/rygel,GNOME/rygel,GNOME/rygel,Pelagicore/Media-Manager-Rygel-patched,jku/rygel,Pelagicore/Media-Manager-Rygel-patched