stack-1.6.3.1 should build with latest hpack (#3294)
stack-1.6.3.1 should build with latest hpack (#3294)

fixes #3294

simonmichael/stackage,mstksg/stackage,mrkkrp/stackage,spencerjanssen/stackage,garetxe/stackage,iand675/stackage,mgajda/stackage,stackbuilders/stackage,clinty/stackage,creichert/stackage,ethercrow/stackage,Shimuuar/stackage,int-index/stackage,asr/stackage,fimad/stackage,athanclark/stackage,jonschoning/stackage,michalkonecny/stackage,fpco/stackage,phaazon/stackage,massysett/stackage,lwm/stackage,Daniel-Diaz/stackage,wereHamster/stackage,soenkehahn/stackage,peti/stackage