Non-evaluated error message in ASSERT

[Scott E. Fahlman <Fahlman@CMU-CS-C.ARPA>]

If there are no objections to the proposed change to the syntax of
ASSERT, I propose that we let Guy decide whether this "erratum" can go
into the manual at this point without undue disruption of the
proofreading/editing/production process.  While changing anything that
is widely used would be unacceptable to us at this time, ASSERT is not
currently being used much in our code, and the proposed change is
trivial.  CHECK-TYPE would also be changed to eval its string, but this
change is upward-compatible, or nearly so.  Guy should give us a clear
go/no-go decision on this change as soon as possible.

I do remember Moon's query on this, and also that I didn't think very
long about its implications, given the amount of stuff that was being
dealt with just then.

-- Scott