Changed builderDefs to use composedArgsAndFun, reduced number of nulls, made overrides in builderDefsPackage to work in an intuitive manner.

svn path=/nixpkgs/trunk/; revision=12655

pkgs/development/libraries/libextractor/0.5.18.nix

@@ -1,5 +1,5 @@
 args : with args;
-	let localDefs = builderDefs {
+	let localDefs = builderDefs.meta.function {
 		src = /* put a fetchurl here */
 		fetchurl {
 			url = http://gnunet.org/libextractor/download/libextractor-0.5.18.tar.gz;
@@ -8,7 +8,7 @@ args : with args;
 
 		buildInputs = [ zlib];
 		configureFlags = [];
-	} null; /* null is a terminator for sumArgs */
+	};
 	in with localDefs;
 stdenv.mkDerivation rec {
 	name = "libextractor"+version;