src/class-utilities.lisp: Permit `temporary-name' objects as class names.

src/class-utilities.lisp: Permit `temporary-name' objects as class names.

This will be helpful in error recovery.  Classes and various related
objects must have names, but if we can't parse the user's choice of name
then we have to make one up.  The easy approach, to avoid conflicts with
the user's other choices, is to pick a name with funny characters in,
but that's properly rejected by the check here; but we can wrap the name
up in a `temporary-name' object to push it through without trouble.