add missing Date methods in es53

es53.js is missing some UTC Date methods that are in the es5 spec.
this adds them.

in particular, toUTCString is needed by jquery.cookie.js

[MarkM, 2012-02-27 22:54:59]

As long as you're doing this, you might want to consider fixing
http://code.google.com/p/google-caja/issues/detail?id=1362 at the same time.

[felix8a, 2012-02-28 12:59:47]

On 2012/02/27 22:54:59, MarkM wrote:
> As long as you're doing this, you might want to consider fixing
> http://code.google.com/p/google-caja/issues/detail?id=1362 at the same time.

hm, no, I'll do that later.  this is "get jquery working".

[metaweta, 2012-02-28 20:22:01]

lgtm

[felix8a, 2012-02-28 23:43:02]

@r4792