* Classes are now tracked past removal from the core container, and module
   removal is actively prevented until all references are freed.
 * A hanging reference stored in the channel has been removed.  This could have
   caused a mismatch and the music state not properly cleared, if two or more
   reloads occurred between MOH being stopped and MOH being restarted.
 * In certain circumstances, duplicate classes were possible.
 * A race existed at reload time between a process being killed and the thread
   responsible for reading from the related pipe respawning that process.
 * Several reference counts have also been corrected.  At least one could have
   caused deleted classes to stick around forever, consuming resources.  This
   originally manifested as MOH external processes that were not killed at
   reload time.
(closes issue #16279, closes issue #16207)
 Reported by: parisioa, dcabot
 Patches: 
       20091202__issue16279__2.diff.txt uploaded by tilghman (license 14)
 Tested by: parisioa, tilghman


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@232660 65c4cc65-6c06-0410-ace0-fbb531ad65f3