Add missing gtk-doc markup, note when args can be NULL to ignore.
Add missing gtk-doc markup, note when args can be NULL to ignore.

noonien-d/wocky,freedesktop-unofficial-mirror/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky