mentioned Php Windows bug in Math.NaN (fixed issue #1469)

std/Math.hx

@@ -66,6 +66,10 @@ extern class Math
 		
 		If this constant is converted to an Int, e.g. through Std.int(), the
 		result is unspecified.
+		
+		(Php) In PHP versions prior to 5.3.1 VC 9 there may be unexpected
+		results when performing arithmetic operations with NaN on Windows, see:
+			https://bugs.php.net/bug.php?id=42143
 	**/
 	static var NaN(default, null) : Float;