Merged revisions 225243 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

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  r225243 | dvossel | 2009-10-21 15:58:08 -0500 (Wed, 21 Oct 2009) | 13 lines
  
  IAX2: VNAK loop caused by signaling frames with no destination call number
  
  It is possible for the PBX thread to queue up signaling frames before
  a destination call number is received.  This can result in signaling
  frames being sent out with no destination call number. Since recent
  versions of Asterisk require accurate destination callnumbers for all
  Full Frames, this can cause a VNAK loop to occur.  To resolve this
  no signaling frames are sent until a destination callnumber is received,
  and destination call numbers are now only required for iax_pvt matching
  when the frame is an ACK.
  
  Review: https://reviewboard.asterisk.org/r/413/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@225307 65c4cc65-6c06-0410-ace0-fbb531ad65f3