bug#31726: Acknowledgement (haskell-mode fails to build with (at least) Emacs 26.1)

[Jack Hill]

It looks like this may be fixed in upstream commit 
cee22450ee30e79952f594796721dc6b17798ee6 [0], which has not ended up in a 
release. I have not verified yet, but it looks like commit would address 
the problem.

[0] 
https://github.com/haskell/haskell-mode/commit/cee22450ee30e79952f594796721dc6b17798ee6