Teach Windows build about the _weakref module.

Modules/_weakref.c

@@ -728,7 +728,7 @@ weakref_functions[] =  {
 };
 
 
-void
+DL_EXPORT(void)
 init_weakref(void)
 {
     PyObject *m;

PC/config.c

@@ -43,6 +43,7 @@ extern void init_locale(void);
 #endif
 extern void init_codecs(void);
 extern void initxreadlines(void);
+extern void init_weakref(void);
 
 /* XXX tim: what's the purpose of ADDMODULE MARKER? */
 /* -- ADDMODULE MARKER 1 -- */
@@ -95,6 +96,7 @@ struct _inittab _PyImport_Inittab[] = {
 
         {"_codecs", init_codecs},
 	{"xreadlines", initxreadlines},
+	{"_weakref", init_weakref},
 
 /* XXX tim: what's the purpose of ADDMODULE MARKER? */
 /* -- ADDMODULE MARKER 2 -- */

PCbuild/pythoncore.dsp

@@ -195,6 +195,21 @@ SOURCE=..\Modules\_localemodule.c
 # End Source File
 # Begin Source File
 
+SOURCE=..\Modules\_weakref.c
+
+!IF  "$(CFG)" == "pythoncore - Win32 Release"
+
+!ELSEIF  "$(CFG)" == "pythoncore - Win32 Debug"
+
+!ELSEIF  "$(CFG)" == "pythoncore - Win32 Alpha Debug"
+
+!ELSEIF  "$(CFG)" == "pythoncore - Win32 Alpha Release"
+
+!ENDIF 
+
+# End Source File
+# Begin Source File
+
 SOURCE=..\Objects\abstract.c
 
 !IF  "$(CFG)" == "pythoncore - Win32 Release"