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/plat-mac/aepack.py b/Lib/plat-mac/aepack.py
index 3caf2f5..e958b85 100644
--- a/Lib/plat-mac/aepack.py
+++ b/Lib/plat-mac/aepack.py
@@ -98,7 +98,7 @@
         return AE.AECreateDesc(b'long', struct.pack('l', x))
     if isinstance(x, float):
         return AE.AECreateDesc(b'doub', struct.pack('d', x))
-    if isinstance(x, (bytes, str8)):
+    if isinstance(x, (bytes, buffer)):
         return AE.AECreateDesc(b'TEXT', x)
     if isinstance(x, str):
         # See http://developer.apple.com/documentation/Carbon/Reference/Apple_Event_Manager/Reference/reference.html#//apple_ref/doc/constant_group/typeUnicodeText