Fix findings from check-in on r374177

Richard pointed out two problems with the check-in from r374177:
* The ast_msg_shutdown function declaration doesn't match the prototype
  in main/message.c.
* The ref/alloc function usage in astobj2 (in trunk) can use the ao2_t_*
  variants of the functions to allow the REF_DEBUG flag to enable/disable
  their debug counterparts.
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Merged revisions 374210 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 374211 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374213 65c4cc65-6c06-0410-ace0-fbb531ad65f3