the parameters  input types are  compatible with Unify.f.   Apply (if
necessary) the resulting substitution to the output parameters.

Also,  when checking array  concat, try  to unify  the types  of both
arrays instead of just checking their equality.

This of course triggers some errors in the non-reg tests.  One of
this error is due to a bug in the parser, where the list of parameter
was inversed twice. I've also fixed that in this change.