Update do_dmqmc_spawning_attempt with correct intent for qmc_state_t.
Update do_dmqmc_spawning_attempt with correct intent for qmc_state_t.

The interface to the excitation generators was changed in private whilst
the DMQMC main algorithm was refactored in public.

hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande