Fix compiling error in MSVS

Need to include math.h before tmmintrin.h in some versions of MSVS.

Change-Id: Ia6b83ae599316887ecf30c4e4b9e4355fb8a4219

vp9/common/x86/vp9_idct_intrin_ssse3.c

@@ -8,6 +8,11 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#if defined(_MSC_VER) && _MSC_VER <= 1500
+// Need to include math.h before calling tmmintrin.h/intrin.h
+// in certain versions of MSVS.
+#include <math.h>
+#endif
 #include <tmmintrin.h>  // SSSE3
 #include "vp9/common/x86/vp9_idct_intrin_sse2.h"