main/formats: Fix crash in ast_format_cmp during non-clean shutdown.

* Update asterisk.h to reflect availability of ast_register_cleanup in 11.9.
* Use ast_register_cleanup for format_attr_shutdown.

(closes issue ASTERISK-23103)
Reported by: JoshE
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Merged revisions 411310 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 411311 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@411312 65c4cc65-6c06-0410-ace0-fbb531ad65f3