Change reference to execframes to naming.

Doc/ref/ref7.tex

@@ -416,7 +416,7 @@ A class definition defines a class object (see section \ref{types}):
 A class definition is an executable statement.  It first evaluates the
 inheritance list, if present.  Each item in the inheritance list
 should evaluate to a class object.  The class's suite is then executed
-in a new execution frame (see section \ref{execframes}), using a newly
+in a new execution frame (see section \ref{naming}), using a newly
 created local namespace and the original global namespace.
 (Usually, the suite contains only function definitions.)  When the
 class's suite finishes execution, its execution frame is discarded but