Make chan_h323 respect packetization settings

Make chan_h323 respect packetization settings

Previously, packetization settings were ignored and now they are not. A new
config option 'autoframing' has been added to mirror the way chan_sip handles
it. Turning on the autoframing option (available both as a global option or per
peer) overrides the local settings with the remote packetization settings.
Testing was performed with varying packetization levels with the following
codecs: ulaw, alaw, gsm, and g729.

(closes issue #12415)
Reported by: pj
Patches:
      2009012200_h323packetization.diff.txt uploaded by mvanbaak (license 7),
      modified by me

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@189991 65c4cc65-6c06-0410-ace0-fbb531ad65f3