fix playground benchmarks

* moved benchmark examples into a subdir "sunspider"
* all the benchmark examples relied on including a script
    <script src="sunspider-record-result.js"></script>
  I'm not clear how the cajoler is supposed to resolve those
  relative links; deferring that to later.  for now I'm just
  inlining the record() function.
* date-format-xparb relies extensively on eval(), it defines functions
  using eval.  it woulld need to be completely rewritten to work, so I
  just removed it from the list of examples.
* date-format-tofte uses eval() to run functions in the local scope.
  I replaced that eval with a lookup table.
* date-format-tofte tries to verify if Date#getFullYear works, in a
  way that fails if you're in the wrong timezone, and then falls back
  to getYear, which is deprecated, and not available in es53.  the code
  should be using Date#getUTCFullYear, but for some reason none of the UTC
  methods are whitelisted in es53.js (maybe pending implementation of
  compatibility shims?)  I changed the benchmark so that the getFullYear
  test succeeds.
* date-format-tofte uses Date#setTime, which for some reason didn't
  get whitelisted in es53.js, so I added it to the whitelist.  afaik
  setTime works on all browsers, so it doesn't need a compatibility shim.
* string-tagcloud tries to define Object.prototype.toJSONString, which
  fails.  I ripped out all that code and used the JSON object instead.
* string-validate-input tries to assign some globals without declaring
  them, which fails in es53, so I added 'var'.

with this change, every benchmark example works for me (though it's
not clear if all the benchmarks work correctly, which is a problem with
sunspider itself.)

[Jasvir, 2011-03-23 21:43:44]

LGTM