Teach Windows how to build the new weakref module.
diff --git a/PCbuild/pythoncore.dsp b/PCbuild/pythoncore.dsp
index 48949cd..4525e6b 100644
--- a/PCbuild/pythoncore.dsp
+++ b/PCbuild/pythoncore.dsp
@@ -1737,6 +1737,21 @@
# End Source File
# Begin Source File
+SOURCE=..\Objects\weakrefobject.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=..\Modules\xreadlinesmodule.c
!IF "$(CFG)" == "pythoncore - Win32 Release"