This patch also fully qualifies some realized types and constructors to
avoid inadvertent shadowing.

This patch also implements a precedence system for printing types.

This removes lots of superfluous parentheses in the outer terms.

Extraction of C arrays

See merge request !88

Improve goals generated by the Gappa printer.

See merge request !103

Rework numerical constants.

See merge request !101

Main changes are:
- Real constants now offer a normalized representation usable for internal
  computations.
- Constants are no longer stored in textual form.

Put the three_idem example in the examples folder

See merge request !99

Factor abnormal transformation exceptions under is_fatal

Closes #275

See merge request !98

Also replace eprintf with Warning.emit in session_itp.

When reloading, fatal transformations should be notified to the user but
should not make the whole reload fail

Add the example about three-idempotent rings

See merge request !97

fix #274

Closes #274

See merge request !96