Insert blank after REFER (bug #997)

Correct path to VM sample (bug #994)
Make manager interface non-blocking (bug #861)
Don't bork on empty from in SIP (bug #887)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@2138 65c4cc65-6c06-0410-ace0-fbb531ad65f3