Merge p3yk branch with the trunk up to revision 45595. This breaks a fair
number of tests, all because of the codecs/_multibytecodecs issue described
here (it's not a Py3K issue, just something Py3K discovers):
http://mail.python.org/pipermail/python-dev/2006-April/064051.html

Hye-Shik Chang promised to look for a fix, so no need to fix it here. The
tests that are expected to break are:

test_codecencodings_cn
test_codecencodings_hk
test_codecencodings_jp
test_codecencodings_kr
test_codecencodings_tw
test_codecs
test_multibytecodec

This merge fixes an actual test failure (test_weakref) in this branch,
though, so I believe merging is the right thing to do anyway.
diff --git a/Python/traceback.c b/Python/traceback.c
index 6c11cf5..cfbd833 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -39,24 +39,16 @@
 static int
 tb_traverse(PyTracebackObject *tb, visitproc visit, void *arg)
 {
-	int err = 0;
-	if (tb->tb_next) {
-		err = visit((PyObject *)tb->tb_next, arg);
-		if (err)
-			return err;
-	}
-	if (tb->tb_frame) 
-		err = visit((PyObject *)tb->tb_frame, arg);
-	return err;
+	Py_VISIT(tb->tb_next);
+	Py_VISIT(tb->tb_frame);
+	return 0;
 }
 
 static void
 tb_clear(PyTracebackObject *tb)
 {
-	Py_XDECREF(tb->tb_next);
-	Py_XDECREF(tb->tb_frame);
-	tb->tb_next = NULL;
-	tb->tb_frame = NULL;
+	Py_CLEAR(tb->tb_next);
+	Py_CLEAR(tb->tb_frame);
 }
 
 PyTypeObject PyTraceBack_Type = {
@@ -165,7 +157,7 @@
 				}
 				if (PyString_Check(v)) {
 					size_t len;
-					len = PyString_Size(v);
+					len = PyString_GET_SIZE(v);
 					if (len + 1 + taillen >= MAXPATHLEN)
 						continue; /* Too long */
 					strcpy(namebuf, PyString_AsString(v));