I've modified the code so that rather than calling `error` to signal an
empty list queue, it calls `raise`, passing a unique object.  This can
be checked using `empty-list-queue-error?` on the object when it is caught.

I've uploaded the revised SRFI and implementation to the staging area.

--
John Cowan          http://www.ccil.org/~cowan        xxxxxx@ccil.org
Original line from The Warrior's Apprentice by Lois McMaster Bujold:
"Only on Barrayar would pulling a loaded needler start a stampede toward one."
English-to-Russian-to-English mangling thereof: "Only on Barrayar you risk to
lose support instead of finding it when you threat with the charged weapon."