AST-2012-007: Fix IAX receiving HOLD without suggested MOH class crash.

* Made schedule_delivery() set the received frame f->data.ptr to NULL if 
the datalen is zero.  

* Fix queue_signalling() memcpy() size error.

* Made queue_signalling() not use C++ keyword variable names.

(closes issue ASTERISK-19597)
Reported by: mgrobecker
Patches:
      jira_asterisk_19597_v1.8.patch (license #5621) patch uploaded by rmudgett
Tested by: rmudgett, Michael L. Young
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Merged revisions 367781 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 367782 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@367783 65c4cc65-6c06-0410-ace0-fbb531ad65f3