Change definitions and names of operations on objects whose type is

Change definitions and names of operations on objects whose type is
`delayed'.  Old name for such objects was `delayed-evaluation', new
name is `promise'.  The microcode has been extended to allow a new
kind of `promise', distinguished by a fixnum zero in its car, whose
cdr is a procedure of no arguments which is applied to get the value.
This is used to support compiled promises.