fix compile errors on older versions of Cabal
Merge pull request #81 from bennofs/fix-compile-errors

fix compile errors on older versions of Cabal
rename dependency on gtk+-3.0 to gtk3
Merge pull request #82 from Fuuzetsu/gtk3

haskell-gtk3: fix generated pkgConfDeps
Distribution/NixOS/Fetch.hs: cosmetic
fetchWith: don't swallow stderr output from sub-processes