(sgml-font-lock-keywords-1): Ignore comments.

(sgml-font-lock-keywords-1): Ignore comments.
(sgml-font-lock-keywords-2): Use `eval'.  Moved from sgml-mode-common.
(sgml-font-lock-syntactic-keywords): New var.
(sgml-mode-common): Drop the two args.
Don't make buffer-local variables that aren't used.
Don't set sgml-font-lock-keywords-2 now that it uses `eval instead.
Don't set `before-string' props from sgml-display-text.
(sgml-mode): Use define-derived-mode.
(sgml-tags-invisible): Use sgml-display-text.
(sgml-quote): New command.
(html-tag-alist): Add args for `span'.
(html-mode): Use define-derived-mode.
Set sgml-display-text and sgml-tag-face-alist.