Reject multiple headers of the same type.
Reject multiple headers of the same type.

A common application pattern is to call vorbis_synthesis_headerin()
 and count how many times it succeeds.
If you feed it multiple valid comment headers, they will all
 succeed, meaning you can be fooled into think you have a valid
 Vorbis file despite never seeing a setup header.
This patch makes libvorbis reject multiple headers of the same type,
 preventing this from occurring.


git-svn-id: 03f0f1727258f1959b7b485b30a676bafdb78148@19426 0101bb08-14d6-0310-b084-bc0e0c8e3800

ShiftMediaProject/vorbis,pcwalton/vorbis,libninjam/libvorbis,pcwalton/vorbis,jdm/vorbis,Rillke/vorbis,pcwalton/vorbis,jdm/vorbis,Rillke/vorbis,libninjam/libvorbis,pcwalton/vorbis,brion/vorbis,jdm/vorbis,ShiftMediaProject/vorbis,libninjam/libvorbis,pcwalton/vorbis,libninjam/libvorbis,brion/vorbis,jdm/vorbis,ShiftMediaProject/vorbis,ShiftMediaProject/vorbis,brion/vorbis,ShiftMediaProject/vorbis,Rillke/vorbis,brion/vorbis,ShiftMediaProject/vorbis,jdm/vorbis,Rillke/vorbis