wmaker: add clip mouse wheel action to change workspace

This patch is adding mouse wheel action on clip to switch from
one workspace to another. It's a modified version of the vinelinux.org
(WindowMaker-0.95.6-wheel.diff) which was setting the action on the entire dock.

THIS PATCH WAS MODIFIED BY Rodolfo García Peñas (kix) because cannot be
applied in the awmaker git without changes. This patch is based in the
original patch created by David Maciejak <david.maciejak@gmail.com>
util: create custom GNUSTEP dir if needed

This patch is creating the missing custom GNUSTEP dir.
Patch found on vinelinux.org as WindowMaker-0.95.6-GSDIR.patch.