(Type Predicates): Document `atom' type.

man/cl.texi

@@ -735,6 +735,11 @@ The type symbol @code{null} represents the symbol @code{nil}.
 Thus @code{(typep @var{object} 'null)} is equivalent to
 @code{(null @var{object})}.
 
+@item
+The type symbol @code{atom} represents all objects that are not cons
+cells. Thus @code{(typep @var{object} 'atom)} is equivalent to
+@code{(atom @var{object})}.
+
 @item
 The type symbol @code{real} is a synonym for @code{number}, and
 @code{fixnum} is a synonym for @code{integer}.