Upgrade Samba supplimentary ports to the new build system. Effectively they are
dependent now from Python 3.4+ for the build, unless NO_PYTHON is specified,
in which case ports still can be build with Python 2.7.
That should address legacy Python dependencies for some non-Samba ports as well.
Update Samba4* supplimentary libraries to the newer versions.
Made databases/ldb to depend on openldap-sasl-client, so it won't conflict with
the corresponding requirement of net/samba4* ports.