ghc 9.8

[andreasabel]

This addresses the -x-partial warning where feasible, using Data.List.NonEmpty. This is an incentive to move to GHC 8 which first had this module in base. Thus, GHC 7 will be dropped.

TODO:

• Remove now redundant #ifs
• Update the Win/Mac CI to GHC 9.8.1
• Reorganize commits
• Fix release date in CHANGELOG

Content:

• gitignore TAGS file
• v3.4.0.1: Address x-partial warning of GHC 9.8
• Drop support for building with GHC 7
• Drop legacy modules Map, Set, Sort
• Drop CPP pertaining to GHC < 8

Candidate at: https://hackage.haskell.org/package/alex-3.4.0.1/candidate
Docs at: https://haskell-alex--247.org.readthedocs.build/en/247/

[andreasabel]

@Ericson2314 : If you want a quick look...

This PR raises to bar to build alex to GHC 8 for the sake of using Data.List.NonEmpty. The latter helps to properly address the new x-partial warnings for head and tail in GHC 9.8.
On the way, I could get rid of pre-containers legacy modules (Set, Map, Sort). We are using containers already so this is not a big step.
Not sure if anyone cares about GHC 7 builds. One could take an older version of alex if one wants to do archeology...

To commits are to be merged as such.
I'll merge and release then...