Fix an obscure but terrible bug in the simplifier (Trac #9567)
The issue was that contInputType simply gave the wrong answer for type applications. There was no way to fix contInputType; it just didn't have enough information. So I did this: * Split the ApplyTo constructor of SimplUtils.SimplCont into ApplyToVal ApplyToTy I used record syntax for them; we should do this for some of the other constructors too. * The latter carries a sc_hole_ty, which is the type of the continuation's "hole" * Maintaining this type meant that I had do to something similar for SimplUtils.ArgSpec. * I renamed contInputType to contHoleType for consistency. * I did a bit of refactoring around the call to tryRules in Simplify, which was jolly confusing before. The resulting code is quite nice now. And it has the additional merit that it works. The tests are simply tc124 and T7891 with -O enabled.