Those helpers were just setting up some extra functions that can be used
on templates, and this can be done already via environment, so let's remove
the helpers completely.
The prepare-32bit hook has been moved to the pre-pkg stage and now
those hooks are executed as part of the install phase. That means that
pre-pkg hooks are now independently run for the subpkgs and the sourcepkg
after the install-destdir phase and pre/do/install hooks.
As bonus, finally correct rdeps can now be collected for the 32bit pkgs
and works for all them, without the need to sort the order of subpkgs!
