Add back mpi-hs (closes #5278)
Add back mpi-hs (closes #5278)

simonmichael/stackage,Daniel-Diaz/stackage,massysett/stackage,iand675/stackage,athanclark/stackage,asr/stackage,fpco/stackage,jonschoning/stackage,michalkonecny/stackage,soenkehahn/stackage,clinty/stackage,mrkkrp/stackage