substring-vector-null-fill!, colitis, etc.

[Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>]

1) I vote to change the grammar to only allow the final ELSE case.
It does not seem like a very large change.

2) VECTOR-FILL! and STRING-FILL! are completely symmetric.  They both
must exist internally for the MAKE-STRING and MAKE-VECTOR procedures.
FLush both or keep both, but I vote to flush both since they can be
written using VECTOR-SET! and STRING-SET!

3) I think that except in a few cases, it is not necessary to agree on
default exactness in the number syntax.  Anybody who is going to use
advantage of it (whenever somebody implements it), will certainly want
to force the exactness/inexactness of his/her explicit numerals by
using prefixes, and nobody else will care, probably.

The only case that must be decided, in my opinion, is making things
like 3, 123, -456 ("obvious" integers) exact, so they can be used as
indeces to VECTOR-MUMBLE and STRING-MUMBLE.

Thus some implementations could agree to be compatible with CL, and
some to take a completely different approach, but the most common case
(and needed by non-numeric code) would be compatible.

4) I like alphabetic colon, and dislike the CL package system too, but
giving up colon seems like a very minor issue.  There are too many
people trying to make a dual CL/Scheme environment, and we should not
make this job harder than it has to be.  Thus I vote moving colon to
unspecified.