Update to new Local channel documentation.

Add same changes as commit to 1.4, but convert to TeX.

(issue #16963)
Reported by: kobaz
Patches: 
      localchannel-2.txt uploaded by kobaz (license 834)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@253256 65c4cc65-6c06-0410-ace0-fbb531ad65f3