PITCH_SHIFT dialplan function

The PITCH_SHIFT function can be used on a channel to independently
modify the pitch of both rx and tx audio streams.  Now you can
improve your conference calls by assigning a random pitch effect
to everyone entering a meetme room, or just make your day more
interesting by making your co-workers sound funny.  These are just
some of the numerious practical uses for this function. Enjoy!

https://reviewboard.asterisk.org/r/526/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@251038 65c4cc65-6c06-0410-ace0-fbb531ad65f3