Get test to build with MSVC

Added _USE_MATH_DEFINES to make sure M_PI can be refered to definitions
in math.h for MSVC

Change-Id: Idca128910384593a002eb08bae72c739fb998e19

test/vp10_txfm_test.h

@@ -13,6 +13,9 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#ifdef _MSC_VER
+#define _USE_MATH_DEFINES
+#endif
 #include <math.h>
 
 #include "third_party/googletest/src/include/gtest/gtest.h"