OpenACC Github PR#499 defines the pqr-list as having at least 1 item. We
already handle that for all but 'wait', so this patch just does the work
to add it for 'wait', plus adds tests.
This is once again simply enabling this for 'data', 'enter data', and
'exit data' (and ensuring we error for 'host_data'). Implementation is
very simply to enable it rather than emit the not-implemented
diagnostic.
