Quantify unfixed kind variables in CUSKs

Authored by goldfire on Jun 14 2018, 7:50 AM.

Description

Quantify unfixed kind variables in CUSKs

This is a small change in user-facing behavior. When we
have a unification variable left over in a CUSK, we previously
would issue an error. But, we can just quantify. This also
teaches kcLHsQTyVars to use quantifyTyVars instead of its own,
ad-hoc quantification scheme.

Fixes Trac #15273.

test case: polykinds/T11648b