Reinstate workarounds for atan2, fmod, pow in MathExtras on vs2013

Source/wtf/MathExtras.h

Index: Source/wtf/MathExtras.h
diff --git a/Source/wtf/MathExtras.h b/Source/wtf/MathExtras.h
index c4945061e8d2f732a22e99cb69b4b6ce88faf839..42ff1224ad354e230628feacc550786470b1866d 100644
--- a/Source/wtf/MathExtras.h
+++ b/Source/wtf/MathExtras.h
@@ -116,7 +116,12 @@ inline float log2f(float num)
 }
 #endif
 
-#if COMPILER(MSVC) && (_MSC_VER < 1800)
+#if COMPILER(MSVC)
+
+// VS2013 has most of the math functions now, but we still need to work
+// around various differences in behavior of Inf.
+
+#if _MSC_VER < 1800
 
 namespace std {
 
@@ -132,6 +137,8 @@ inline float nextafterf(float x, float y) { return x > y ? x - FLT_EPSILON : x +
 
 inline double copysign(double x, double y) { return _copysign(x, y); }
 
+#endif // _MSC_VER
+
 // Work around a bug in Win, where atan2(+-infinity, +-infinity) yields NaN instead of specific values.
 inline double wtf_atan2(double x, double y)
 {
@@ -165,6 +172,8 @@ inline double wtf_pow(double x, double y) { return y == 0 ? 1 : pow(x, y); }
 #define fmod(x, y) wtf_fmod(x, y)
 #define pow(x, y) wtf_pow(x, y)
 
+#if _MSC_VER < 1800
+
 // MSVC's math functions do not bring lrint.
 inline long int lrint(double flt)
 {
@@ -187,6 +196,8 @@ inline long int lrint(double flt)
     return static_cast<long int>(intgr);
 }
 
+#endif // _MSC_VER
+
 #endif // COMPILER(MSVC)
 
 inline double deg2rad(double d)  { return d * piDouble / 180.0; }