kdbus.h: add ULL suffix to shifted 64-bit values
kdbus-test: add --wait and --bus parameters
test/kdbus-util.c: reduce message size for tests
kdbus.h: comment
metadata, queue: remove all namespace translating hacks again

After carefully revisiting the entire namespace translation ideas
again, we concluded that what we're currently doing doesn't possibly
cover all use cases that we have in mind.

a) We want to be able to do create a connection inside a container,
   pass the file handle to it to the outside world, and expect to be
   operating from inside the container with it. Namespace translation
   is not on in such cases.

b) While we can map pids and uids from inside a namespace into
   something that is meaningful on the host, the other way around is
   impossible: if we pass a handle from the host into the container,
   namespace translation cannot succeed.

As user namespaces aren't something we need to support anytime soon
anyway, the easiest solution for now is to remove all the current
code again and remove the metadata from the final message in case
we're jumping across namespaces with it.
metadata: rename domain → pid_namespace
metadata: add kdbus_meta_ns_eq()

Pin the user ns as well, and introduce kdbus_meta_ns_eq() to check
whether all namespaces of a kdbus_meta objects are equal.
update kdbus.txt
test/test-metadata-ns: tweak test to reflect recent changes
fix typos in kdbus.txt