Fix floating point issues on Windows.

runtime/platform/c99_support_win.cc

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file

[Mads Ager (google), 2012/11/28 09:26:26]

Just move your new implementation to c99_support_win.h as a static inline
function?

[aam-me, 2012/11/28 12:14:36]

Done.

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include <math.h>
+
+#include "platform/c99_support_win.h"
+
+double round(double x) {
+  if (!_finite(x)) {
+    return x;
+  }
+
+  double intpart;
+  double fractpart = modf(x, &intpart);
+
+  if (fractpart >= 0.5) {
+    return intpart + 1;
+  } else if (fractpart > -0.5) {
+    return intpart;
+  } else {
+    return intpart - 1;
+  }
+}