Fix builds for ghc-7.6.*, ghc-7.7*, ghc-7.8.*
Fix builds for ghc-7.6.*, ghc-7.7*, ghc-7.8.*

	Tested the following combinations:
	ghc 7.6.3, Cabal 1.16.0
	ghc 7.8.3, Cabal 1.18.1.3
	ghc 7.8.3, Cabal 1.24.0.0 (*)
	ghc 7.10.1, Cabal 1.22.2.0
	ghc 7.10.1, Cabal 1.24.0.0 (*)

    * For some reason I had to use --constraint=Cabal=1.24.0.0
      to get configure to select these.

pacak/hdevtools,takano-akio/hdevtools,ranjitjhala/hdevtools,hdevtools/hdevtools