sounds: Fix Sounds Makefile and XML that didn't support new sound prompt sets
In sounds/Makefile
1 Adds and moves some lines necessary for the en_GB core set. I'm just following how the other sets are defined here.
2 removes the ES extra sounds related lines as we don't have ES extra sound sets.
In sounds/sounds.xml
3 Adds member definitons for EN_AU, EN_GB, IT for core sound sets, and EN_GB in extra sound sets
ASTERISK-23550 #close
Review: https://reviewboard.asterisk.org/r/3464/
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Merged revisions 412586 from http://svn.asterisk.org/svn/asterisk/branches/11
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@412587
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