Test more versions of GHC on CI

[sol]

No description provided.

[sol]

@RyanGlScott are you ok with renaming master to main?

7.2.1 seems to be failing because of some SafeHaskell issue. This is something we might want to fix, if possible.

[sol]

Same for 7.4.1, SafeHaskell. I disabled fail-fast for now, so that we see which minor versions have issues.

All the versions that were tested on Travis work fine (I had a good build for them before https://github.com/haskell-compat/base-compat/actions/runs/526141035).

[sol]

I opened #72. It tests the versions of GHC that we had on Travis + it's ready to merge. This PR enables more GHCs and can be considered separately.

[RyanGlScott]

If I recall correctly, the build failures all concern the base-compat-batteries package in particular. Before #65, when I gave up on the idea of trying to maintain CI for every minor release of GHC, I maintained this collection of hacks to support particular minor releases of GHC. It's likely that many of the issues you encounter here were also documented in that collection of hacks.