SF patch# 1770008 by Christian Heimes (plus some extras).
Completely get rid of StringIO.py and cStringIO.c.

I had to fix a few tests and modules beyond what Christian did, and
invent a few conventions.  E.g. in elementtree, I chose to
write/return Unicode strings whe no encoding is given, but bytes when
an explicit encoding is given.  Also mimetools was made to always
assume binary files.
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index d98c607..c016681 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -1,7 +1,7 @@
 import unittest
 from test import test_support
 
-import sys, UserDict, cStringIO
+import sys, UserDict
 
 
 class DictTest(unittest.TestCase):