ConfigParser:
- ensure that option names in interpolations are handled by
  self.optionxform in the same way that other references to option
  names
- add tests, documentation
(closes SF bug #857881, patch #865455)
diff --git a/Lib/test/test_cfgparser.py b/Lib/test/test_cfgparser.py
index b1b495e..28063b5 100644
--- a/Lib/test/test_cfgparser.py
+++ b/Lib/test/test_cfgparser.py
@@ -222,11 +222,11 @@
             "with11=%(with10)s\n"
             "with10=%(with9)s\n"
             "with9=%(with8)s\n"
-            "with8=%(with7)s\n"
-            "with7=%(with6)s\n"
+            "with8=%(With7)s\n"
+            "with7=%(WITH6)s\n"
             "with6=%(with5)s\n"
-            "with5=%(with4)s\n"
-            "with4=%(with3)s\n"
+            "With5=%(with4)s\n"
+            "WITH4=%(with3)s\n"
             "with3=%(with2)s\n"
             "with2=%(with1)s\n"
             "with1=with\n"