This fixes builds after #4419. Thanks to @vbgl for the original commit;
I changed that as I'm not sure whether passing null values to buildInputs is clean.
CC maintainers: @coroa, @peti, @phreedom, @robberer, @jcumming.
`selectVersion ./foo "bar"' instead of `import ./foo/bar.nix'.
* Replaced `with args' with formal function arguments in several
packages.
* Renamed several files to `default.nix'. As a general rule, version
numbers should only be included in the filename when there is a
reason to keep multiple versions of a package in Nixpkgs.
Otherwise, it just makes it harder to update the package.
svn path=/nixpkgs/trunk/; revision=18403
