print_proof now prints s subtypes, even when these are variables
print_proof now prints s subtypes, even when these are variables

Information was lost with the previous version, which resulted in too
much s(_) types.

There is now a print_proof/4 predicate which allows us to print s
subtype variables as ‘_’, just as before (this is used by
transform_proof.pl

RichardMoot/GrailLight