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/Python/mactoolboxglue.c b/Python/mactoolboxglue.c
index 0714cff..454553e 100644
--- a/Python/mactoolboxglue.c
+++ b/Python/mactoolboxglue.c
@@ -194,7 +194,7 @@
 PyMac_BuildOSType(OSType t)
 {
 	uint32_t tmp = htonl((uint32_t)t);
-	return PyBytes_FromStringAndSize((char *)&tmp, 4);
+	return PyString_FromStringAndSize((char *)&tmp, 4);
 }
 
 /* Convert an NumVersion value to a 4-element tuple */