Backported PyCapsule from 3.1, and converted most uses of
CObject to PyCapsule.
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index fbd0239..d44a691 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -4496,7 +4496,7 @@
 
 	/* Export C API */
 	if (PyModule_AddObject(m, PySocket_CAPI_NAME,
-	       PyCObject_FromVoidPtr((void *)&PySocketModuleAPI, NULL)
+	       PyCapsule_New(&PySocketModuleAPI, PySocket_CAPSULE_NAME, NULL)
 				 ) != 0)
 		return;