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/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@429204 f38db490-d61c-443f-a65b-d21fe96a405b