Update core-spec for Coercion Quantification

Authored by ningning on Oct 25 2018, 9:01 AM.

Description

Update core-spec for Coercion Quantification

Summary:
Update details for ForAllTy and ForAllCo in core-spec, as they
can now quantify over coercion variables.

Test Plan: Please read core-spec.pdf

Reviewers: goldfire, simonpj, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, carter

GHC Trac Issues: Trac #15497, Trac #15589

Differential Revision: https://phabricator.haskell.org/D5247