Rehabilitate autotest.py.
In README: Write up (Guido's) rules for intra-test imports; warn against
asserts; document test_support.use_large_resources.
diff --git a/Lib/test/autotest.py b/Lib/test/autotest.py
index ba85a0d..57f371b 100644
--- a/Lib/test/autotest.py
+++ b/Lib/test/autotest.py
@@ -1,3 +1,6 @@
-# Backward compatibility -- you should use regrtest instead of this module.
+# This should be equivalent to running regrtest.py from the cmdline.
+# It can be especially handy if you're in an interactive shell, e.g.,
+# from test import autotest.
+
import regrtest
regrtest.main()