add CPU_COUNT and cpu_set_t Change-Id: I9b92cab27a8bb4fda71a99721801013647e02588 Reviewed-on: https://review.haiku-os.org/c/haiku/+/9618 Reviewed-by: Jérôme Duval <[email protected]> Reviewed-by: waddlesplash <[email protected]> Tested-by: Commit checker robot <[email protected]>