samba: remove cifs-utils tools from build systems

samba: remove cifs-utils tools from build systems

Now that cifs-utils are their own project, we need to go ahead and pull
them out of the samba tree. This patch represents the first step toward
that end.

Remove the cifs-utilities from the source3 and source4 builds. Please
pay particular attention to the source4 piece. I'm not at all familiar
with the build system there, and would appreciate someone sanity
checking my changes.

It also adds a small README.cifs-utils file in the topdir. This is
optional, but I think it's a good idea to carry this for a release or
two.

Once this patch looks ok, I'll plan to do another patch to actually
remove the client dir and the relevant docs-xml files from the tree
altogether.

Signed-off-by: Jeff Layton <jlayton@redhat.com>