Private branch to track experimental implementation of enforcing SIP username uniqueness. 


git-svn-id: http://scm.sipfoundry.org/rep/sipX/branches/sipXconfig_unique_sip_usernames@5065 a612230a-c5fa-0310-af8b-88eea846685b
Address extension uniqueness by putting all SIP usernames in a single user_name table.  Check this code into a side branch because it turned out to be too complicated, but it's worth keeping it around for reference.


git-svn-id: http://scm.sipfoundry.org/rep/sipX/branches/sipXconfig_unique_sip_usernames@5066 a612230a-c5fa-0310-af8b-88eea846685b