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/xmlrpclib.py b/Lib/xmlrpclib.py
index efb0a7b..da96420 100644
--- a/Lib/xmlrpclib.py
+++ b/Lib/xmlrpclib.py
@@ -622,7 +622,7 @@
         write("<value><string>")
         write(escape(value))
         write("</string></value>\n")
-    dispatch[str8] = dump_string
+    dispatch[bytes] = dump_string
 
     def dump_unicode(self, value, write, escape=escape):
         write("<value><string>")