elm genlist: Added comments for dragging flag.
elm genlist: Added comments for dragging flag.

Signed-off-by: Daniel Juyung Seo <seojuyung@gmail.com>

SVN revision: 68649

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