Revert: this breaks compiles in Linux, by using the local Vorbis source

(which we only use in Win32) instead of the system headers.

The correct fix is to add "vorbis" to the include file path in the Xbox
project, like we do in the Windows project.

stepmania/src/RageSoundReader_Vorbisfile.cpp

@@ -9,9 +9,9 @@
 #include "RageLog.h"
 
 #if defined(INTEGER_OGG)
-#include "tremor/ivorbisfile.h"
+#include <tremor/ivorbisfile.h>
 #else
-#include "vorbis/vorbis/vorbisfile.h"
+#include <vorbis/vorbisfile.h>
 #endif
 
 #if defined(_XBOX)