Allow class to be isolated

Part of #599

lang/spec.html

@@ -8510,7 +8510,7 @@ <h3>Module class definition</h3>
    [<code>public</code>] class-type-quals <code>class</code> identifier <code>{</code>
       class-member*
   <code>}</code>
-class-type-quals := (<code>distinct</code> | <code>readonly</code> | object-network-qual)*
+class-type-quals := (<code>distinct</code> | <code>readonly</code> | isolated-qual | object-network-qual)*
 class-member :=
    object-field
    | method-defn
@@ -8535,6 +8535,15 @@ <h3>Module class definition</h3>
 only if its read-only bit is set.
 </p>
 <p>
+If <code>class-type-quals</code> contains <code>isolated</code>, then the
+defined object type is an isolated type, and an object constructed using the
+type will have its isolated bit set. An <code>object-field</code> or
+<code>method-defn</code> occurring as a <code>class-member</code> in an isolated
+class is subject to same requirements as when it occurs as an
+<code>object-member</code> in an <code>object-constructor-expr</code> that is
+explicitly isolated.
+</p>
+<p>
 If an object-type-inclusion references a type-descriptor that is a class, then
 only the type of the class is included: the definitions of the methods and any
 initializers for the fields are not included. If a class uses an