avx ifdef for scale HAS_SCALEADDROW_AVX2.

R=jzern@google.com
BUG=libyuv:480

Review URL: https://webrtc-codereview.appspot.com/53779004.

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1455
+Version: 1456
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 1455
+#define LIBYUV_VERSION 1456
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/scale_win.cc

@@ -826,6 +826,7 @@ void ScaleAddRow_SSE2(const uint8* src_ptr, uint16* dst_ptr, int src_width) {
   }
 }
 
+#ifdef HAS_SCALEADDROW_AVX2
 // Reads 32 bytes and accumulates to 32 shorts at a time.
 __declspec(naked)
 void ScaleAddRow_AVX2(const uint8* src_ptr, uint16* dst_ptr, int src_width) {
@@ -854,6 +855,7 @@ void ScaleAddRow_AVX2(const uint8* src_ptr, uint16* dst_ptr, int src_width) {
     ret
   }
 }
+#endif  // HAS_SCALEADDROW_AVX2
 
 // Bilinear column filtering. SSSE3 version.
 __declspec(naked)