Add authentication options to the SIP dialstring.

Documentation follows separately

(issue #11587)
Reported by: sobomax
Patches: 
      chan_sip.c-trunk.diff uploaded by sobomax (license 359)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@99521 65c4cc65-6c06-0410-ace0-fbb531ad65f3