Moved link generation routine from setup.py to release.py. The new routine requires Python 2.6 for izip_longest and chain.from_iterable, so it's not suitable for setup.py. Also, there's no reason that every installer needs to compute the links - they can be resolved in advance during the release process.

--HG--
branch : distribute
extra : rebase_source : 9f4af99f70fdfa00290be2261a921af9a76ba597