Implement an iterator framework for uid and thread data. Iterators
ensure that the underlying data is accessed in the right order and
provide an abstraction of the index handling.
Iterators should be used when the order of the uids/threads is
important.
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>
