This allows access to the sqlstate and ought to get rid of the
confused transaction state bug.

Closes #12, closes #13.

By materializing a single regexp from all lines in known_re, the CPU
load by filtering goes down by 90%.

Closes #12.

This can be sorted, making updating them more lightweight because
diffs are smaller and probably also GIT's delta compression works
better.

Suggested by @zesoup.

It is now down to the 20% of the old type system.

This allows modelling type compatibility beyond equality.