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: http://svn.asterisk.org/svn/asterisk/branches/12@405124 f38db490-d61c-443f-a65b-d21fe96a405b
Use proper case for checking if digest authentication is used.



git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@405131 f38db490-d61c-443f-a65b-d21fe96a405b