Revert higher rank polymorphism for now
This branch removes support for RankNTypes
and depends on curry-base!18 (merged).
The idea here is to defer support for higher-rank polymorphism due to longer-standing issues in the frontend (see #77) and focus on having a stable main version of the frontend again.
A future merge request could re-revert these changes to include higher-rank-polymorphism support again.
Edited by Fredrik Wieczerkowski