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/copy.py b/Lib/copy.py
index fa75daa..1a14f0e 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -187,7 +187,7 @@
     d[complex] = _deepcopy_atomic
 except NameError:
     pass
-d[str8] = _deepcopy_atomic
+d[bytes] = _deepcopy_atomic
 d[str] = _deepcopy_atomic
 try:
     d[types.CodeType] = _deepcopy_atomic