Benchmark script execution performance.

It would be nice to include in the benchmark scripts some benchmarks of the scripts after they are minified to also account for optimisations.

Minimal:

* Run time for a single function that gives high coverage.
* If it's a standard JS lib being tested, run it's own included tests as a benchmark?

OTT?

* Run time for a variety of functions.
* More detailed timings (min/max/avg).
* Memory/CPU usage.

Throw in the full INTL / ICU lib for fun?