ogg/vorbis/opus: Make them modules and unbundle thirdparty libs

Took the opportunity to undo the Godot changed made to the
opus source. The opus module should eventually be built in its
own environment to avoid polluting others with too many include
dirs and defines.

TODO: Fix the platform/ stuff for opus.

thirdparty/libvorbis/window.h

@@ -0,0 +1,26 @@
+/********************************************************************
+ *                                                                  *
+ * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
+ * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
+ * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
+ * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
+ *                                                                  *
+ * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2007             *
+ * by the Xiph.Org Foundation http://www.xiph.org/                  *
+ *                                                                  *
+ ********************************************************************
+
+ function: window functions
+ last mod: $Id: window.h 19028 2013-12-02 23:23:39Z tterribe $
+
+ ********************************************************************/
+
+#ifndef _V_WINDOW_
+#define _V_WINDOW_
+
+extern const float *_vorbis_window_get(int n);
+extern void _vorbis_apply_window(float *d,int *winno,long *blocksizes,
+                          int lW,int W,int nW);
+
+
+#endif