Fix specification error that makes it impossible for 'reload()' to work

correctly with PEP 302 module loaders.  See also SF#1029475, and:

http://mail.python.org/pipermail/python-dev/2004-September/048970.html

pep-0302.txt

@@ -240,16 +240,22 @@ Specification part 1: The Importer Protocol
     The load_module() method has a few responsibilities that it must
     fulfill *before* it runs any code:
 
-    - It must create the module object.  From Python this can be done
+    - It must use the existing module object from sys.modules, if one
+      exists.  (Otherwise, the reload() builtin will not work
+      correctly.)
+
+    - If a module object is not already present in sys.modules, the
+      loader must create a module object.  From Python this can be done
       via the new.module() function, the imp.new_module() function or
       via the module type object; from C with the PyModule_New()
       function or the PyImport_ModuleAdd() function.  The latter also
       does the following step:
 
-    - It must add the module to sys.modules.  This is crucial because
-      the module code may (directly or indirectly) import itself; adding
-      it to sys.modules beforehand prevents unbounded recursion in the
-      worst case and multiple loading in the best.
+    - It must add the module to sys.modules, if it was not already
+      present there.  This is crucial because the module code may 
+      (directly or indirectly) import itself; adding it to sys.modules
+      beforehand prevents unbounded recursion in the worst case and
+      multiple loading in the best.
 
     - The __file__ attribute must be set.  This must be a string, but it
       may be a dummy value, for example "<frozen>".  The privilege of