Add allow_uncaught_exception to onerror tests so that they run properly.
Merge pull request #440 from zcorpan/fix-onerror-uncaught-exception

Add allow_uncaught_exception to onerror tests so that they run properly.
Replace assert_null and assert_not_null with assert_equals and assert_not_equals.
Replaced assert_not_undefined and assert_not_null with assert_not_equals.
Also changed the expected result for cloneNode() as its default value has been changed from true to false.
Use .html extension instead of .xht extension inside html-templates/additions-to-the-css-user-agent-style-sheet
since they're not valid XHTML documents (e.g. missing html element) and need to be parsed as HTML documents.
Merge pull request #442 from rniwa/remove_assert_null_from_parsing_html_templates

Replace assert_null and assert_not_null with assert_equals and assert_not_equals.
Merge pull request #443 from rniwa/use-html-extension-for-tests-in-html-templates

Use .html extension instead of .xht extension inside html-templates/additions-to-the-css-user-agent-style-sheet