Allow isolated with service-decl

Part of #599.

lang/spec.html

@@ -8381,7 +8381,7 @@ <h4>Service declaration</h4>
 
 <pre
 class="grammar">service-decl :=
-   metadata
+   metadata [isolated-qual]
    <code>service</code> [[type-descriptor] variable-name] <code>on</code> expression-list object-constructor-block
 expression-list := expression (<code>,</code> expression)*
 </pre>
@@ -8400,7 +8400,9 @@ <h4>Service declaration</h4>
 <code>attach</code> method of L. The object-constructor-block has the same
 semantics as in an object-constructor-expr with a <code>service</code> qualifier
 and a type-reference that refers to S. The type S is also used as the type of
-the variable declared.
+the variable declared. If the service-decl includes <code>isolated</code>, then
+it is equivalent to an object-constructor-expr with an <code>isolated</code>
+qualifier as well as a <code>service</code> qualifier.
 </p>
 <p>
 A service-decl is initialized as part of module initialization as follows. The