Combine the functionality of test_support.run_unittest()
and test_support.run_classtests() into run_unittest()
and use it wherever possible.

Also don't use "from test.test_support import ...", but
"from test import test_support" in a few spots.

From SF patch #662807.
diff --git a/Lib/test/test_filecmp.py b/Lib/test/test_filecmp.py
index 282cba6..0e5f297 100644
--- a/Lib/test/test_filecmp.py
+++ b/Lib/test/test_filecmp.py
@@ -119,10 +119,7 @@
 
 
 def test_main():
-    suite = unittest.TestSuite()
-    for cls in FileCompareTestCase, DirCompareTestCase:
-        suite.addTest(unittest.makeSuite(cls))
-    test_support.run_suite(suite)
+    test_support.run_unittest(FileCompareTestCase, DirCompareTestCase)
 
 if __name__ == "__main__":
     test_main()