Maclisp compatibility

[DLW at MIT-AI (Daniel L. Weinreb)]

The Lisp Machine implements Maclisp "single-character objects" as
symbols, but, as opposed to what it says in the Lisp Machine manual,
they are not interned in the USER package; in reality, they are interned
in the current package, whatever it is.  The system had been
inconsistent about this; in particular, READCH was wrong.  A recent
system patch fixes READCH so that it will return symbols in the current
package rather than the USER package.  If this affects your programs,
you may want to fix them.  JLK says this will not break Macsyma.