Fix incorrect documentation of the MailboxStatus manager command.

The "Waiting" field was misdocumented as reporting the number of
messages waiting. In reality, it simply indicated the presence or
absence of waiting messages.
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Merged revisions 371782 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 371783 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 371784 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@371785 65c4cc65-6c06-0410-ace0-fbb531ad65f3