testInsertBefore(): Rewritten to actually test insertBefore() somewhat.

testInsertBefore():  Rewritten to actually test insertBefore() somewhat.

testAAA(),
testAAB():  Added checks that the results are right.

testTooManyDocumentElements():  Added code to actually test this.

testCloneElementDeep()
testCloneElementShallow():  Filled these in with test code.

_testCloneElementCopiesAttributes(),
_setupCloneElement():  Helper functions used with the other
        testCloneElement*() functions.

testCloneElementShallowCopiesAttributes():  No longer a separate test;
        _setupCloneElement() uses _testCloneElementCopiesAttributes() to
        test that this is always done.

testNormalize():  Added to check Node.normalize().