0.8.1.48

0.8.1.48
	Significantly rearrange locking code for thread waitqueues, to
	eradicate races shown up in McCLIM applications.  It's better
	than it was, and I can't trigger the lockup any longer: I
	don't claim it's _correct_, just that I can no longer see
	anything wrong with it

	Tidy up some constants in sb-bsd-sockets

	Amend spec in SB-POSIX to deal better with the differences
	between a CL namestring and a string-representing-a-filename-
	as-known-to-the-OS