This function is now called fallback-dds-build-state-graph-edges and
it is parameterised by a function which produces the next states with
annotations (like dds-one-step-annotated). The functions
dds-build-state-graph and dds-build-n-step-state-graph now fall back
to calling fallback-dds-build-state-graph-edges, passing it the
function dummy-annotated-dds-step-one to add a 'dummy annotation to
each new state produced.
