Merge the code from asterisk/team/group/chan_unistim:

This introduces a new channel driver, chan_unistim, that supports the Unistim
VoIP protocol for Nortel phones.  The following models have been confirmed 
to work: i2002, i2004 and i2050.

(closes issue #8864)
Reported by: c_hans
Patches: 
      chan_unistim.patch uploaded by c (license 304)
      ustm_no_conf.diff uploaded by junky (license 177)
Tested by: c_hans, dbowerman, math, junky, loloski


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@88368 65c4cc65-6c06-0410-ace0-fbb531ad65f3