Re-enable testing of mmark and mmark-ext
Re-enable testing of mmark and mmark-ext

I believe I have fixed the test suites. New versions of the packages have
been released.

iand675/stackage,simonmichael/stackage,mrkkrp/stackage,michalkonecny/stackage,jonschoning/stackage,Daniel-Diaz/stackage,fpco/stackage