fileselector: Added @since 1.8 for new APIs
fileselector: Added @since 1.8 for new APIs

4c7285d add new APIs but missed "@since 1.8"
Spotted by Hermet.

FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary