Add support for building against pjproject with SIP transaction group lock support.

(issue ASTERISK-22818)
Reported by: Matt Jordan
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Merged revisions 402864 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402865 f38db490-d61c-443f-a65b-d21fe96a405b