Used by the routines at upd_128_to_130, adj_m4_m12, upd_6_7, upd_10, upd_11, upd_12_to_15, adj_m8_m12, adj_m7_m12, adj_m12_m12, upd_88_to_90, adj_p7_m12 and adj_p3_m12.

The offset routines from upd_128_to_130 to adj_p3_m12 all end by jumping here, because set_pixel_adj is too far away for a relative jump and a JR plus one shared JP is shorter than a JP in every one of them.