TODO

Consider having elements that suppress reopening
Handle namespace declarations semi-properly
Squelch namespaces better in --nons mode
Clean systemids as well as publicids

Notice: It's quite possible that none of these features will ever be
implemented.  If you'd like to implement one yourself, feel free to send
me a patch.

Flag added parent elements with a special attribute
Allow case sensitivity as a standard feature
Make use of the pseudo-comment in a script element to suppress close-tag detection
Allow inline cruft in table bodies and rows
	(Don't break up tables, ever?)
	(Don't break up forms, ever, either?)
Suppress start-tags for some restartable elements if the element
	is already on the stack (<b><b> is the same as <b>)
Combine consecutive body elements