X64/Win64: Alternative implementation of fmod in general.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index b8fe96726cc10913c27186e48a60eb1d02a7c28d..1e1245c5d15562b43ff33f1f6fd3abfd2f67e49b 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -54,6 +54,12 @@
 namespace v8 {
 namespace internal {
 
+// ----------------------------------------------------------------------------
+// Math functions
+
+double modulo(double x, double y) {
+  return fmod(x, y);
+}
 
 // ----------------------------------------------------------------------------
 // POSIX date/time support.