Log message:
make it clear what package depend on

discussed with wiz@.

Log message:
Import zlib-0.5.4.1 as archivers/hs-zlib,
packaged for wip by pho.

This package provides a pure interface for compressing and decompressing
streams of data represented as lazy ByteStrings. It uses the zlib C library
so it has high performance. It supports the "zlib", "gzip" \ 
and "raw"
compression formats.

It provides a convenient high level API suitable for most tasks and for the
few cases where more control is needed it provides access to the full zlib
feature set.