So, I have removed all of the uses of AST_LIST_HEAD_INIT and replaced them
   with the equivalent static initializations.
 - On passing, fix a memory leak in the unload_module() function of chan_agent.
   The agents list mutex was never destroyed, and the elements in the agents
   list were not freed.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@26990 65c4cc65-6c06-0410-ace0-fbb531ad65f3