Fix the frozen bytecode for __hello__ (betcha didn't know that existed
:-).

Add a test that prevents the __hello__ bytecode from going stale
unnoticed again.

The test also tests the loophole noted in SF bug #404545.  This test
will fail right now; I'll check in the fix in a minute.
diff --git a/Lib/__phello__.foo.py b/Lib/__phello__.foo.py
new file mode 100644
index 0000000..8e8623e
--- /dev/null
+++ b/Lib/__phello__.foo.py
@@ -0,0 +1 @@
+# This file exists as a helper for the test.test_frozen module.