Blocked revisions 281185 via svnmerge

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  r281185 | dvossel | 2010-08-06 16:34:38 -0500 (Fri, 06 Aug 2010) | 20 lines

  chan_sip: fixes provisional keepalive scheduled item crash

  There is a scheduler item in chan_sip that keeps sending the
  last provisional message in response to an INVITE Request for
  a period of time until a final response to that INVITE is
  sent.  Because of the way this scheduler item works, it requires
  a reference to a sip_pvt pointer to work properly.  The problem
  with this is that it is currently possible (but rare) for the
  sip_pvt to get destroyed and that scheduler item to still
  exist.  When this occurs, the scheduler event fires and attempts
  to access a freed sip_pvt which causes a crash.

  (closes issue #17497)
  Reported by: anonymouz666
  Patches:
        keepalive_diff_1.4_v2.diff uploaded by dvossel (license 671)

  Review: https://reviewboard.asterisk.org/r/849/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@281186 65c4cc65-6c06-0410-ace0-fbb531ad65f3