Add Data.Void to base

Last year I proposed adding Data.Void, with a canonical uninhabited type Void, to base. This would replace the module of the same name in Edwardk Kmett's void package (and in turn he'll update his package to reëxport the module from base).

The response to the proposal was mostly positive; there were a couple of objections to the name, but Void is so standard by now that it seems pointless to change it, and no better name was suggested. Unfortunately I never did anything about it at the end of the discussion period. Recently several people have asked me to move this proposal along, and I'm finally getting around to making the ticket. Hopefully it can happen before the 7.10 freeze.

Trac metadata

Trac field	Value
Version	7.8.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
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Blocking
CC	core-libraries-committee@haskell.org
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Architecture