More feedback from Symbolics reviewers

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

In the current version of the document, CALL-NEXT-METHOD is documented
as a macro.  That was a mistake; it should be a function.  The document
should be updated.  We'll do it next time we get the lock on the document,
unless someone else does it first, which would be perfectly okay with me.

The Remarks field of CALL-NEXT-METHOD should say that it can only be
called from the lexical scope of the body of a DEFMETHOD or DEFMETHOD-SETF.
The current documentation sort of implies this but doesn't say it explicitly.
In most implementations CALL-NEXT-METHOD will be defined with a FLET 
that DEFMETHOD wraps around its body, rather than being a global function,
and maybe the Remarks field should mention this.

In the Possible Extensions field of CALL-NEXT-METHOD, the sentence that
discusses APPLY-NEXT-METHOD should be deleted.  Regular APPLY can be used
now that it is a function.

Making it a function instead of a macro makes it slightly more difficult
for implementations to optimize it, but not significantly more difficult.
It makes the semantics simpler and more consistent with the rest of Lisp.

Does anyone object to these changes?