Remove/deprecate HTMLBlockElement & HTMLPhraseElement

[danielnixon]

HTMLBlockElement and HTMLPhraseElement don't appear in any of the specs and I can't conjure either of them in Firefox. Searching the web suggests they're IE-specific implementation details that may or may not still exist in recent versions of IE.

[sjrd]

PR welcome.

[aappddeevv]

block should be blockquote