gnome-rr: add API to check whether rotation is supported

Export a method on GnomeRROutputInfo to check which rotation options are
supported.

https://bugzilla.gnome.org/show_bug.cgi?id=721672
build: bump version

Since we added new API

https://bugzilla.gnome.org/show_bug.cgi?id=721672
docs: update gnome-desktop3-sections.txt

https://bugzilla.gnome.org/show_bug.cgi?id=721672