#168: type(): Unequal stack element types always compare unequal.
Issue #168: Preparations for list equality check.
Issue #168: Factor out core of equal() into its own non-stack-using function.
Issue #168: Implement/use the actual list comparison functionality.
Merge branch 'feature/168-list-equal' into intertarget-code
Merge branch 'intertarget-code' of github.com:SWP-Ubau-SoSe2014-Haskell/SWPSoSe14 into intertarget-code