add rtp-autoflush profile param and rtp_autoflush var to skip timer sleeps when the socket has data ready and refactor the jitter buffer code out into a different function and fix it so it works in blocking mode too

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@12854 d0543943-73ff-0310-b7d9-9358b9ac24b2