Correct output of RTCP jitter statistics in SR and RR reports

Change the RTCP RR and SR generation code to convert Asterisk's internal jitter
statistics to be represented in RTP timestamp units based on the rate of the
codec in use instead of in seconds.

(closes issue ASTERISK-14530)
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Merged revisions 351611 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 351612 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@351613 65c4cc65-6c06-0410-ace0-fbb531ad65f3