Merged revisions 279949 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

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  r279949 | dvossel | 2010-07-27 15:57:00 -0500 (Tue, 27 Jul 2010) | 31 lines
  
  Merged revisions 279946 via svnmerge from 
  https://origsvn.digium.com/svn/asterisk/branches/1.6.2
  
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    r279946 | dvossel | 2010-07-27 15:54:32 -0500 (Tue, 27 Jul 2010) | 24 lines
    
    Merged revisions 279945 via svnmerge from 
    https://origsvn.digium.com/svn/asterisk/branches/1.4
    
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      r279945 | dvossel | 2010-07-27 15:33:40 -0500 (Tue, 27 Jul 2010) | 19 lines
      
      remove empty audiohook write list on channel
      
      If a channel has an audiohook write list created on it, that
      list stays on the channel until the channel is destroyed.  There
      is no reason to keep that list on the channel if it becomes empty.
      If it is empty that just means we are doing needless translating
      for every ast_read and ast_write.  This patch removes the audiohook
      list from the channel once it is detected to be empty on either a
      read or write.  If a audiohook is added back to the channel after
      this list is destroyed, the list just gets recreated as if it never
      existed to begin with.
      
      (closes issue #17630)
      Reported by: manvirr
      
      Review: https://reviewboard.asterisk.org/r/799/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@279951 65c4cc65-6c06-0410-ace0-fbb531ad65f3