Need to sanitize Date code to ensure we adhere to ES5 15.9.1.14

• Component: JavaScriptCore
• Status: NEW ---

[Mark Lam]

So far, we've added strategic checks on the time milliseconds value in the Date object.  However, the spec is unclear about whether that limit applies to the UTC time, or Local time, or both.  Currently, we conservatively clip the value for both.

We also don't have a guarantee that we've done adequate limit checks to ensure we don't have underflow / overflow issues in the Date math code.  It would be great if there's something we can do to ensure that we don't silently underflow / overflow in the math thereby resulting in bogus Date strings.