Merging the py3k-pep3137 branch back into the py3k branch.
No detailed change log; just check out the change log for the py3k-pep3137
branch.  The most obvious changes:

  - str8 renamed to bytes (PyString at the C level);
  - bytes renamed to buffer (PyBytes at the C level);
  - PyString and PyUnicode are no longer compatible.

I.e. we now have an immutable bytes type and a mutable bytes type.

The behavior of PyString was modified quite a bit, to make it more
bytes-like.  Some changes are still on the to-do list.
diff --git a/Lib/test/buffer_tests.py b/Lib/test/buffer_tests.py
index 01ac3c5..db27759 100644
--- a/Lib/test/buffer_tests.py
+++ b/Lib/test/buffer_tests.py
@@ -1,11 +1,11 @@
-# Tests that work for both str8 (bytes) and bytes (buffer) objects.
+# Tests that work for both bytes and buffer objects.
 # See PEP 3137.
 
 import struct
 import sys
 
 class MixinBytesBufferCommonTests(object):
-    """Tests that work for both str8 (bytes) and bytes (buffer) objects.
+    """Tests that work for both bytes and buffer objects.
     See PEP 3137.
     """