The queue gets filled by the tail, so a query will always be the tail
object, not the head object. Also add a _peek_tail_struct() method to the
GstQueueArray to enable looking at the tail.
With unit test to prevent future regression.
https://bugzilla.gnome.org/show_bug.cgi?id=762875
This way we don't have to allocate/free temporary structs
for storing things in the queue array.
API: gst_queue_array_new_for_struct()
API: gst_queue_array_push_tail_struct()
API: gst_queue_array_peek_head_struct()
API: gst_queue_array_pop_head_struct()
API: gst_queue_array_drop_struct()
https://bugzilla.gnome.org/show_bug.cgi?id=750149
This is a queue which has the same API as GQueue, except that:
* It uses an array, instead of a doubled-linked-list
* The array can only grow.
This code is not-threadsafe. It is up to the owner to make sure the
proper locking is taken before calling this API.
