This updates the version of rnix used and refactors the code generally
to be more precise and capable in it's identification of both lambdas
and determining which documentation comments are attached.
Change-Id: Ib0dddabd71f772c95077f9d7654023b37a7a1fd2
package.nix previously needed this callPackage'd externally, which
didn't make a lot of sense to us since this is an internal dependency.
Thus we changed it to make it more self contained.
Change-Id: I4935bc0bc80e1a132bc9b1519e917791da95037c