This also changes the versioning scheme to be in more "human-meaningful"
terms, so instead of the internal release numbers we talk about 10.10.5
or 10.9.5.
`nix-env -qaP -A pkgs.darwin`
pkgs.darwin.libutil:
Commented-out because the package definition doesn't exist. The source
doesn't even provide a Makefile...
pkgs.darwin.objc4_pure:
Commented-out because the package is broken and referencing unknown
applefetchsource and libc_old names. It doesn't seem to be used by any
other packages too.
