NOTE: THIS VERSION IS STILL EXPERIMENTAL.   The API is VERY likely to
be changed before the final version.

Originally written by Rui Ueyama.  The original (pure Scheme) version
is kept as peg-orig.scm for a reference; it is cleaner than the current
optimized version so it'd be easier to understand.

benchmark.scm and prof.scm are for tuning.  They use a sample data file
data/13tokyo.cvs, which is a public domain data provided by Japanese
Postal Service.


