meraculous: Convert to new overlay system

pkgs/all-packages.nix

@@ -3,4 +3,6 @@ self: pkgs: with pkgs; {
   cryptominisat = callPackage ./cryptominisat.nix { };
 
   firedrake = callPackage ./firedrake { };
+
+  meraculous = callPackage ./meraculous.nix { };
 }

pkgs/meraculous.nix

@@ -1,4 +1,5 @@
-with import <nixpkgs> { };
+{ stdenv, overrideCC, gcc49, fetchurl, makeWrapper, gzip, cmake
+, boost159, perl, perlPackages, gnuplot }:
 
 # gcc 5.x c++11 requires istream to be explicitly cast to bool