Massive patch by Skip Montanaro to add ":name" to as many
PyArg_ParseTuple() format string arguments as possible.
diff --git a/Modules/structmodule.c b/Modules/structmodule.c
index 9994d20..0a706a9 100644
--- a/Modules/structmodule.c
+++ b/Modules/structmodule.c
@@ -1097,7 +1097,7 @@
 	const formatdef *f;
 	int size;
 
-	if (!PyArg_ParseTuple(args, "s", &fmt))
+	if (!PyArg_ParseTuple(args, "s:calcsize", &fmt))
 		return NULL;
 	f = whichtable(&fmt);
 	size = calcsize(fmt, f);
@@ -1262,7 +1262,7 @@
 	int len, size, num;
 	PyObject *res, *v;
 
-	if (!PyArg_ParseTuple(args, "ss#", &fmt, &start, &len))
+	if (!PyArg_ParseTuple(args, "ss#:unpack", &fmt, &start, &len))
 		return NULL;
 	f = whichtable(&fmt);
 	size = calcsize(fmt, f);