AMI: Add missing VarSet events when a channel inherits variables.

There should be AMI VarSet events when channel variables are inherited by
an outgoing channel.  Also local;2 should generate VarSet events when it
gets all of its channel variables from channel local;1.

ASTERISK-24415 #close
Reported by: Richard Mudgett
Patches:
      jira_asterisk_24415_v12.patch (license #5621) patch uploaded by Richard Mudgett

Review: https://reviewboard.asterisk.org/r/4074/
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Merged revisions 425782 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 425783 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@425784 65c4cc65-6c06-0410-ace0-fbb531ad65f3