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

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  r215682 | twilson | 2009-09-02 16:41:22 -0500 (Wed, 02 Sep 2009) | 18 lines
  
  Re-send non-100 provisional responses to prevent cancellation
  
  From section 13.3.1.1 of RFC 3261:
  
     If the UAS desires an extended period of time to answer the INVITE,
     it will need to ask for an "extension" in order to prevent proxies
     from canceling the transaction. A proxy has the option of canceling
     a transaction when there is a gap of 3 minutes between responses in a
     transaction. To prevent cancellation, the UAS MUST send a non-100
     provisional response at every minute, to handle the possibility of
     lost provisional responses.
  
  (closes issue #11157)
  Reported by: rjain
  Tested by: twilson
  
  Review: https://reviewboard.asterisk.org/r/315/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@215758 65c4cc65-6c06-0410-ace0-fbb531ad65f3