libvpx: Pull from upstream

source/libvpx/vpx_dsp/fastssim.c

Index: source/libvpx/vpx_dsp/fastssim.c
diff --git a/source/libvpx/vp9/encoder/vp9_fastssim.c b/source/libvpx/vpx_dsp/fastssim.c
similarity index 98%
rename from source/libvpx/vp9/encoder/vp9_fastssim.c
rename to source/libvpx/vpx_dsp/fastssim.c
index f1d408cbe7b966dd138d06bc750a7f6bd8d2e92c..1405a30e00af02d932f9c27ea4e3cfbc41f184c8 100644
--- a/source/libvpx/vp9/encoder/vp9_fastssim.c
+++ b/source/libvpx/vpx_dsp/fastssim.c
@@ -11,10 +11,12 @@
  *  project.
  */
 #include <math.h>
+#include <stdlib.h>
 #include <string.h>
 #include "./vpx_config.h"
-#include "./vp9_rtcd.h"
-#include "vp9/encoder/vp9_ssim.h"
+#include "./vpx_dsp_rtcd.h"
+#include "vpx_dsp/ssim.h"
+#include "vpx_ports/system_state.h"
 /* TODO(jbb): High bit depth version of this code needed */
 typedef struct fs_level fs_level;
 typedef struct fs_ctx fs_ctx;
@@ -443,10 +445,11 @@ static double convert_ssim_db(double _ssim, double _weight) {
   return 10 * (log10(_weight) - log10(_weight - _ssim));
 }
 
-double vp9_calc_fastssim(YV12_BUFFER_CONFIG *source, YV12_BUFFER_CONFIG *dest,
+double vpx_calc_fastssim(const YV12_BUFFER_CONFIG *source,
+                         const YV12_BUFFER_CONFIG *dest,
                          double *ssim_y, double *ssim_u, double *ssim_v) {
   double ssimv;
-  vp9_clear_system_state();
+  vpx_clear_system_state();
 
   *ssim_y = calc_ssim(source->y_buffer, source->y_stride, dest->y_buffer,
                       dest->y_stride, source->y_crop_width,