Usage: ddu_set_brccmd(int cmd, DD_BRCCMD_FCN brc_cmd_fcn)
Returns 0 if good status, -1 if bad.
Sets the broadcast command cmd to the function brc_cmd_fcn.
brc_cmd_fcn is a pointer to a function of type DD_BRCCMD_FCN
as defined in dd_dcom.h.
The commands can be defined in dd_usr_brccmd.