Open up generation of keywords to verify it contains the full latin-1 alphabet.
When running profiled benchmarks, run some more rounds.

This fixes eventual problems with tests that complete too quickly under profiling.
Simplify and optimize parse_string/1

* Fold decode_string into decode.
* Optimize parse_string/1 by moving things into one pattern match and rely onthe PM compiler to produce better results.
Inline a couple of simple functions in the rolling cache to speed it up