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_richcmp.py b/Lib/test/test_richcmp.py
index b4fc2ea..5ade8ed 100644
--- a/Lib/test/test_richcmp.py
+++ b/Lib/test/test_richcmp.py
@@ -352,7 +352,7 @@
             self.assertIs(op(x, y), True)
 
 def test_main():
-    test_support.run_classtests(VectorTest, NumberTest, MiscTest, DictTest, ListTest)
+    test_support.run_unittest(VectorTest, NumberTest, MiscTest, DictTest, ListTest)
 
 if __name__ == "__main__":
     test_main()