Cabal-based Haskell ports module

Hey Matthias,

I've been working on this for a while. There's a fairly solid story for
replacing all Haskell binary ports. I also added a few more ports that
previously looked daunting (e.g. pandoc). All the hs-library ports will
be going away. So does the brittle dependency tracking that prevented
easy upgrades.

The current state of affairs is squashed into a stack of patches I
keep on github:
https://github.com/blackgnezdo/ports/commits/ghc810-squashed

All these ports are known to build on amd64 and i386. I have also been
using xmonad and xmobar ports on my main amd64 machine for months now.
I minimally tested the rest of the binaries on amd64.

Let's figure out a good way to get this reviewed and submitted past 6.8
thaw. Some known missing parts are:

* module documentation
* use more of cabal.port.mk for cabal port
* integrated manifest generator (portgen?)
* make test (preferring direct cabal v2-test)

Thanks
Greg