Now I tested and discussed with claude, and had a working version of
this project.  The rest is to port the claude version to my own
writings.  So this serves as the starting point before that attempt.

In the new attempt the design is better, and a number of bugs were
found and supposedly fixed, so let us see how this goes at the end.

* Cargo.toml
* chain/Cargo.toml
* grammar/Cargo.toml: Bump version.

* ChangeLog: Add a short description of the bug fix introduced in this
  version.

Not bug deals but adjustments of details.

I think I should make a new sub-crate dedicated to the tokenization
process instead.

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.

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.

* grammar/src/label.rs (set_end_option): This function replaces the
  old function `open_end`, as this new function is more general than
  the old one, and there is no specific situation where we only need
  to open the end of a node without the need to close the node in an
  `if` statement.

This bug caused a plain unambiguous grammar to become ambiguous.

Funnily enough, this bug revealed a lot of bugs in the code for
handling forests.  I guess this is an unexpected surprise.  :D