Fix voicemail problems when using ogg/vorbis.

Ogg/vorbis was fairly useless as a voicemail file format because it did
not implement the seek and tell format callbacks among other problems.

Since we were already using the libvorbis and libvorbisenc libraries we
can use libvorbisfile as it is also part of the vorbis library package.

* Made use the libvorbisfile to handle the ogg/vorbis file stream.  The
format_ogg_vorbis.c is now mostly a wrapper around libvorbisfile.

(closes issue ASTERISK-16926)
Reported by: sque
Patches:
      ogg_vorbis_use_libvorbisfile.patch (license #6108) patch uploaded by sque
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Merged revisions 355365 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 355375 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@355376 65c4cc65-6c06-0410-ace0-fbb531ad65f3