This change:
- refactors the packages so it is easier to create and update new versions of
cassandra.
- fixes a bug where Cassandra will not connect to another member unless
LD_PRELOADing libstdc++.so. Without that change, it generates a stack trace
and dies with exceptions regarding org.xerial.snappy.
- restricts platform to linux as procps is also linux only.
Upstream likes to move "old" releases to an archive mirror as soon as a
new one is released. This is now handled for free by mirrors.nix.
(No idea why cs.utah.edu was used to begin with; it's now added to
mirrors.nix. Note that it doesn't support SSL, but that applies to
several others so I don't see the harm.)
