Support cabal 2.2

[erikd]

Relatively low priority, but should be done at some point. Hopefully be able to keep compatibility with 1.24.2, and 2.0.

[tmcgilchrist]

Most of the work is done here: #234

Remaining issue is just sorting out the failing chaos integration test.

[andreabedini]

#234 has been merged a year ago, should this issue be closed?