libvpx: Pull from upstream

source/libvpx/vp9/common/vp9_mv.h

Index: source/libvpx/vp9/common/vp9_mv.h
===================================================================
--- source/libvpx/vp9/common/vp9_mv.h	(revision 291857)
+++ source/libvpx/vp9/common/vp9_mv.h	(working copy)
@@ -34,6 +34,14 @@
   int32_t col;
 } MV32;
 
+static INLINE int is_zero_mv(const MV *mv) {
+  return *((const uint32_t *)mv) == 0;
+}
+
+static INLINE int is_equal_mv(const MV *a, const MV *b) {
+  return  *((const uint32_t *)a) == *((const uint32_t *)b);
+}
+
 static INLINE void clamp_mv(MV *mv, int min_col, int max_col,
                             int min_row, int max_row) {
   mv->col = clamp(mv->col, min_col, max_col);