I have fixed another bug and think that the version of a more stable
version is worth bumping the versions for.

Add an intentionally ambiguous grammar for testing purposes.

It seems to work fine.

* nfa/src/default/regex.rs: Previously when merging regular
  expressoins, only the graphs are merged, but the `types` array
  stayed unchanged.  This caused errors of indices being out of
  bounds.

Previously the errors emitted while reading abnf grammars reported
incorrect indices.  Now this is fixed.

This makes it easier if I want to debug things.

This bumping of version is insignificant.  I just find it notable that
I seem to finally obtain a version without trivial bugs.  Hooray!

The chain-rule machine needs a place-holder node at the beginning.
But afterwards that node is pure annoyance and disturbs the
functioning of the machine.  Consequently I removed that node whenever
the right time comes.

This seems to fix some other bugs.  It is reasonable: the presence of
that bogus node is just noise to the machine and error-prone.

* chain/src/atom/default.rs (print_virtual): Previously printing
  virtual nodes is done inside the function `print_nfa`; now this is
  decoupled and thus more flexible.