ARI/AMI: Include language in standard channel snapshot output

ARI/AMI: Include language in standard channel snapshot output

The channel "language" was already part of a channel snapshot, however is was
not sent out over AMI or ARI. This patch makes it so the channel "language" is
included in the appropriate AMI or ARI events.

ASTERISK-24553 #close
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/4245/
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Merged revisions 429204 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 429206 from http://svn.asterisk.org/svn/asterisk/branches/13

git-svn-id: https://origsvn.digium.com/svn/asterisk/certified/branches/13.1@429891 65c4cc65-6c06-0410-ace0-fbb531ad65f3