Allow for multiple contacts to be configured in a single contact= line.

This is useful for configuring multiple permanent contacts for an AOR when using
realtime AORs.

Review: https://reviewboard.asterisk.org/r/3462
........

Merged revisions 412582 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@412584 65c4cc65-6c06-0410-ace0-fbb531ad65f3