libvpx: Add VP9 decoder.

source/libvpx/vp9/decoder/x86/vp9_x86_dsystemdependent.c

+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "vpx_ports/config.h"
+#include "vpx_ports/x86.h"
+#include "vp9/decoder/vp9_onyxd_int.h"
+
+#if HAVE_MMX
+void vp9_dequantize_b_impl_mmx(short *sq, short *dq, short *q);
+
+void vp9_dequantize_b_mmx(BLOCKD *d) {
+  short *sq = (short *) d->qcoeff;
+  short *dq = (short *) d->dqcoeff;
+  short *q = (short *) d->dequant;
+  vp9_dequantize_b_impl_mmx(sq, dq, q);
+}
+#endif
+
+