Actually run these tests from regrtest.py.

There was no test_main() and the main body was protected
by if __name__ == '__main__' so the test didn't happen
on import either.
diff --git a/Lib/test/test_multifile.py b/Lib/test/test_multifile.py
index 6cb946f..cd89e5e 100644
--- a/Lib/test/test_multifile.py
+++ b/Lib/test/test_multifile.py
@@ -56,11 +56,11 @@
         lines = mf.readlines()
         linecount += len(lines)
 
-def main():
+def test_main():
     f = cStringIO.StringIO(msg)
     getMIMEMsg(multifile.MultiFile(f))
     assert boundaries == 2
     assert linecount == 9
 
 if __name__ == '__main__':
-    main()
+    test_main()