Made a change to XHTML5 handling to ensure that the xmlns is specified correctly.
Made a change to XHTML5 handling to ensure that the xmlns is specified
correctly.

Currently doesn't handle aliased html doctypes, such as "<html:html
xmlns:html="...">".

squizlabs/HTML_CodeSniffer,squizlabs/HTML_CodeSniffer,squizlabs/HTML_CodeSniffer