as a lot of index are not computed correctly anymore

* Moved (print_lexp_ctx) from lparse.ml to debruijn.ml to help debugging
* src/lparse.ml: types and expression are processed in a different context

Nevertheles, Macro are still not recognized as such
(back to the original issue)

* src/lexp.ml (sort_level): Replace SLn with SLz.
(lexp_location, _lexp_to_str): Adjust accordingly.

* src/opslexp.ml (sort_level_max): New function.
(sort_compose): Use it.
(impredicative_erase): New var.
(check): Adjust for new SLz.  Obey impredicative_erase.
Fix level calculation for inductive types.

* src/builtin.ml (type0, type1, type2): Adjust.