Fixed #1807: Crash when shutting down library while having subscription transactions on going.




git-svn-id: http://svn.pjsip.org/repos/pjproject@4969 74dad513-b988-da41-8d7b-12977e46ad98
Fixed #1808: Crash in pjsip_inv_terminate() (thanks to Brian Walker for the patch)



git-svn-id: http://svn.pjsip.org/repos/pjproject@4970 74dad513-b988-da41-8d7b-12977e46ad98
Ticket #1809: Fixed DNS SRV resolver bug that application callback may be called twice.



git-svn-id: http://svn.pjsip.org/repos/pjproject@4971 74dad513-b988-da41-8d7b-12977e46ad98