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/fftw/default.nix

@@ -1,5 +1,5 @@
 args : with args;
-	let localDefs = builderDefs { 
+	let localDefs = builderDefs.meta.function { 
 		src = 
 			fetchurl {
 				url = ftp://ftp.fftw.org/pub/fftw/fftw-3.1.2.tar.gz;
@@ -7,7 +7,7 @@ args : with args;
 			};
 		buildInputs = [];
 		configureFlags = ["--enable-float --enable-shared"];
-	} null;
+	};
 	in with localDefs;
 stdenv.mkDerivation {
 	name = "fftw-3.1.2";