bug#4511: 23.1; flyspell-mode slow editing near end of big html file

[Kevin Ryde <user42@zip.com.au>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
> If performance is good enough,

I've been using it, it seems good.  What chance putting it in for
everyone to have a go?

The only thing to note is right now sgml-lexical-context doesn't
recognise <!-- ... --> comments (bug 4781).  But the current
sgml-mode-flyspell-verify code doesn't recognise such comments either,
so nothing is lost.

I think it makes sense to spell check comments.  The net effect of
excluding just "tag" and "pi" parts is that tag and attribute names are
skipped, but basically everything else is checked.  String valued
attributes are checked, which makes sense for

    <img ... alt="Some text">

though string values which are urls might not want checking.  Maybe some
tag/attribute type info could distinguish the two cases, if it seemed
important enough ...