[trac931] corrected the document added in the previous commit a bit.

src/lib/config/ccsession.h

@@ -256,9 +256,9 @@ public:
      * for those changes. This function will subscribe to the relevant module
      * channel.
      *
-     * If the module name is specified (spec_is_filename is false), the
-     * ModuleCCSession must have been constructed with start_immediately
-     * being false and the \c start() method must not have been called.
+     * This method must be called before calling the \c start() method on the
+     * ModuleCCSession (it also implies the ModuleCCSession must have been
+     * constructed with start_immediately being false).
      *
      * \param spec_name This specifies the module to add. It is either a
      *                  filename of the spec file to use or a name of module