Facility to mitigate double-breakage due to Data.Version.versionTag Deprecation

See https://groups.google.com/forum/\#!topic/haskell-core-libraries/q9H-QlL_gnE

Trac metadata

Trac field	Value
Version
Type	Task
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	libraries/base
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ekmett, hvr
Operating system
Architecture

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