pbx_lua: Add support for Lua 5.2

pbx_lua: Add support for Lua 5.2

This adds support for Lua 5.2 in pbx_lua which is available on newer
operating systems.

(closes issue ASTERISK-23011)
Review: https://reviewboard.asterisk.org/r/3075/
Reported by: George Joseph
Patch by: George Joseph
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Merged revisions 405090 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 405091 from http://svn.asterisk.org/svn/asterisk/branches/11

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@405124 65c4cc65-6c06-0410-ace0-fbb531ad65f3