Re-add gi-gtk-hs
Re-add gi-gtk-hs

There is a new revision of gi-gtk-hs-0.3.5.0 in hackage with a relaxed
upper bound on base, better reflecting reality.

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