query: Add new GstQueryInterleaving
Submitted by Seungha Yang
Most elements which have responsibility for posting buffering message
(queue2 or multiqueue) have limited information of A/V stream interleaving.
So, if a container level stream is badly interleaved, the buffering message
posted by the element is unreliable. This "Interleaving" query
can be used for the elements to query actual interleaving of current stream.