Language declaration tests updated

The HTML language declaration tests in the Internationalization Activity test suite have been updated as follows:

• tests were simplified, and now rely only on :lang for language detection
• HTML5 and XHTML5 were added as a new test formats
• tests now use strict DOCTYPEs
• results pages were updated to reflect latest browser version behaviour, and to make it easier to see the assertions used for the tests
• some small errors in the tests were corrected

Other changes behind the scenes include gathering of all tests into a single PHP file (generatehtml.php is no longer used). Code in the PHP file was also streamlined.

The general improvements to the test and results pages mentioned above will be added to other tests over time.