HP 2013 packages shaping up...

[Aleksey Khudyakov]

> criterion & statistics: both require a number of smaller packages we don't
> have like erf and math-functions. Again, will take time to sort out.
>
Few words about statistics & math-functions & mwc-random

Dependency on erf could be easily dropped. It's only used to import erf, erfc
implemented in the libc. Latest release reexport them anyway so it's only
matter of adding FFI imports.

Other non-platform dependencies of statistics:

 * vector-algorithms
 * monad-par
This one have quite big dependency tree. And given bugs [1,2] there could
be problems with inclusion

I also wouldn't consider statistics API very stable. It's very incomplete
featurewise and so major API changes are inevitable.


[1] https://github.com/simonmar/monad-par/issues/21
[2] https://github.com/simonmar/monad-par/issues/23