No commit message

to build an ill-typed formula. Unsafe functions are actually unsafe.

This is less dangerous than I previously thought,
because we still can never create an ill-typed term,
nor we can push a term with an unprotected de Bruijn
index into a context. Salut, François ;)

- export everything to facilitate debugging output
- remove src/pretty.ml*
- restore output/why3.ml to register with Driver a printer from Pretty

No commit message