0.8.20.29:

0.8.20.29:
	Merge SB-FUTEX and SB-THREAD: the latter now requires the
	former.  SBCL threads now require Linux kernel 2.6, or an NPTL
	backport to 2.4 such as the Red Hat one

	Lock/unlock functions take long (not int) as arguments: this makes
	a difference on 64 bit ports (or would do if we had threading support
	on either of them)