Add tests for main/jitterbuf.c

This patch adds unit tests for main/jitterbuf.c.  This includes checking for
the following:
  * Nominal insertion and retrieval of frames
  * Insertion and retrieval of frames where the frames are inserted out of
    order with respect to the previous frame
  * Insertion and retrieval of frames where some number of frames that would
    occur in the expected sequence are instead dropped
  * Insertion and retrieval of frames with an arrival time that does not occur
    at the same rate as the surrounding frames
  * Resynchronization of the jitter buffer when an inserted frame breaks the
    resynchronization threshold
  * Overfilling of the jitter buffer

For each of the tests, both JB_TYPE_VOICE and JB_TYPE_CONTROL permutations
exist.

Review: https://reviewboard.asterisk.org/r/1815

(issue: ASTERISK-18964)
Reported by: Kris Shaw
Tested by: Kris Shaw, Matt Jordan



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@359406 65c4cc65-6c06-0410-ace0-fbb531ad65f3