plugins/elements/gstqueue.*: Refactor an cleanup queue a bit.

plugins/elements/gstqueue.*: Refactor an cleanup queue a bit.

Original commit message from CVS:
* plugins/elements/gstqueue.c: (gst_queue_init),
(gst_queue_finalize), (update_time_level), (apply_segment),
(apply_buffer), (gst_queue_locked_flush),
(gst_queue_locked_enqueue), (gst_queue_locked_dequeue),
(gst_queue_handle_sink_event), (gst_queue_chain),
(gst_queue_push_one), (gst_queue_loop):
* plugins/elements/gstqueue.h:
Refactor an cleanup queue a bit.
Do better time level calculations that also work when the srcpad is not
yet running.
Remove some unneeded debug lines.
* tests/check/elements/queue.c: (GST_START_TEST), (queue_suite):
Added testcase for time level measurement.
Try to make some stuff more racefree.