Add yet another pseudo package which isn't as pseudo as the others:

Add yet another pseudo package which isn't as pseudo as the others:
Arch all packages are now represented by arch depending packages which
all depend on a package with the same name and the special arch "all".
This packages has NO dependencies, but beside this the same information.
It is the only package which has a size, the arch depending ones all
have a zero size. While the arch depending pseudo packages are used
for dependency resolution the arch "all" package is used for downloading
and ordering of the package.