mathematica: add webdoc versions to all-packages

The default mathematica package uses the BNDL version of the installer,
which is much larger and results in a bigger package than the webdoc
version. This change makes it much easier to install the webdoc version.

pkgs/top-level/all-packages.nix

···
 
   mathematica = callPackage ../applications/science/math/mathematica { };
 
+  mathematica-webdoc = callPackage ../applications/science/math/mathematica {
+    webdoc = true;
+  };
+
   mathematica-cuda = callPackage ../applications/science/math/mathematica {
+    cudaSupport = true;
+  };
+
+  mathematica-webdoc-cuda = callPackage ../applications/science/math/mathematica {
+    webdoc = true;
     cudaSupport = true;
   };