This function is used to create a system.
dg_system_t *dg_system_create(dg_sysf_t action);
dg_system_t *render = dg_system_create(&dg_sys_render)
dg_system_t *dg_system_create(dg_sysf_t action)
{
dg_system_t *system = 0;
if (!action)
return 0;
system = malloc(sizeof(dg_system_t));
if (!system)
return 0;
system->system = action;
return system;
}