Add support for HTML5 <input> types.

* Whitelist input type={search,tel,url,email,datetime,date,month,week,
  time,datetime-local,number,range,color}.
* Add properties/methods for numeric field types: stepUp, stepDown,
  step, min, max, valueAsNumber.
* Export assertNaN to guest tests.

Does not work in ES5/3 mode because the cajoler is not allowing the new
types despite the schema change, but we can debug that later.

Fixes <https://code.google.com/p/google-caja/issues/detail?id=1609>.

@r5388

[felix8a, 2013-05-01 02:18:04]

lgtm