Build without warnings (-Wall -Wcompat)

[int-index]

The following warnings should no longer get triggered:

• -Wnoncanonical-monoid-instances
• -Wnoncanonical-monad-instances
• -Wstar-is-type

[int-index]

The CI failure is not related to this patch. The problem is that test-suite aeson is not compatible with newer aeson (could be fixed either by updating the code or adding an upper bound).

I can rebase when this is addressed.

[acowley]

This kind of maintenance is greatly appreciated, thank you! I’ll look into the test suite issue.