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/Tools/framer/example.py b/Tools/framer/example.py
index 96f6278..8a267e9 100644
--- a/Tools/framer/example.py
+++ b/Tools/framer/example.py
@@ -14,7 +14,7 @@
 
     Usage:
 
-    from cStringIO import StringIO
+    from io import StringIO
 
     an_output_stream = StringIO()
     an_output_stream.write(some_stuff)