func_audiohookinherit: Document some missed sources.

This patch also mentions that AUDIOHOOK_INHERIT can be used to
transfer MixMonitor audiohooks. There is also wiki that addresses
audiohooks and the use of AUDIOHOOK_INHERIT at the following link:
https://wiki.asterisk.org/wiki/display/AST/Audiohooks

(closes issue ASTERISK-18220)
Reported by: Ishfaq Malik
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Merged revisions 373467 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 373468 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 373470 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@373479 65c4cc65-6c06-0410-ace0-fbb531ad65f3