Proposal: remove versionTags from Data.Version

[Henning Thielemann]

On Tue, 23 Sep 2014, Thomas Miedema wrote:

> ## Motivation
> * The Eq and Ord instances of Version don't agree whether two versions with different versionTags are equal
> or not [1]:
> 
>     > a = Version [1] ["a"]
>     > b = Version [1] ["b"]
>     > compare a b
>     EQ
>     > a == b
>     False
> 
> * The Package versioning policy does not include version tags [2].
> * Cabal no longer supports package version tags [3,4].


How are versions of pkg-config handled? pkg-config does not always return 
numeric versions.