Add _nrflag definition to stubs_entry.S so it can be used like other stubs values. Update generic/capt_seq.c to optionally use the stubs value (enabled on G12, G1X, IXUS310, SX40 & SX50).
Comment out 'nullsub' calls (G12, G1X, IXUS310, SX30 & SX40).