Kinds as "I don't care" type variables

Let's allow to use kinds as "I don't care"/"it doesn't matter" type variables at function's signature

fst :: (a, *) -> a

This is the same '_' - "i don't care" variable, but in signatures.

fst (a, _ ) = a

And "_" remains as "black hole" at signatures

Trac metadata

Trac field	Value
Version	7.6.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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