Make all of the various rtpqos parameters in this branch available from the CHANNEL function.

Also includes a test for retrieving rtpqos parameters, including a NULL RTP
driver.  Additionally, some further separation of the SIP internal API into
headers was necessary.

(closes issue #16652)
 Reported by: kkm
 Patches: 
       20100204__issue16652.diff.txt uploaded by tilghman (license 14)
 
Review: https://reviewboard.asterisk.org/r/501/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@247124 65c4cc65-6c06-0410-ace0-fbb531ad65f3