Add document numbers for the C99 status page.

Add document numbers for the C99 status page.

This doesn't add all of the document numbers, but it adds a bunch of
them. Not all of the documents are available on the committee page
(they're old enough that they come from a time when the mailing was
comprised of physical pieces of paper), so some of the documents listed
are assumed to be correct based on my reading of editor's reports.