Checkpoint.  Manipulated things so that string literals are always
unicode, and a few other compensating changes, e.g. str <- unicode,
chr <- unichr, and repr() of a unicode string no longer starts
with 'u'.  Lots of unit tests are broken, but some basic things
work, in particular distutils works so the extensions can be built,
and test_builtin.py works.
diff --git a/Python/ast.c b/Python/ast.c
index 8b91894..d7e3b36 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -3187,7 +3187,7 @@
         }
     }
 #ifdef Py_USING_UNICODE
-    if (unicode || Py_UnicodeFlag) {
+    if (!*bytesmode) {
         return decode_unicode(s, len, rawmode, encoding);
     }
 #endif