We are going to loop over the parent array infos.
This introduces a new parent field to permit this loop (patch 40).
Then it will be used to loop over multiple parent ss:
 - gfc_set_loop_bounds_from_array_spec (patch 41 with context diff)
 - gfc_trans_array_constructor (patch 42)
 - set_vector_loop_bounds (patch 43)
OK?