Excise DL_EXPORT/DL_IMPORT from Modules/*.  Required adding a prototype
for Py_Main().

Thanks to Kalle Svensson and Skip Montanaro for the patches.
diff --git a/Modules/gdbmmodule.c b/Modules/gdbmmodule.c
index 6e85ed3..accf438 100644
--- a/Modules/gdbmmodule.c
+++ b/Modules/gdbmmodule.c
@@ -504,7 +504,7 @@
     { 0, 0 },
 };
 
-DL_EXPORT(void)
+PyMODINIT_FUNC
 initgdbm(void) {
     PyObject *m, *d, *s;