Added pretty printing for any function ending with "toString" (any case) of the right type, for displaying counter-examples for the Verification.
Added pretty printing for any function ending with "toString" (any case) of the right type,
for displaying counter-examples for the Verification.

epfl-lara/stainless,epfl-lara/stainless,epfl-lara/stainless,epfl-lara/stainless