Broken XHTML on a lot of xcb manpages

Your XHTML generator generates invalid XHTML document, making a bunch of 
browsers complain about it and cut it off. Some browsers (specifically, 
Firefox), straight up reject rendering those pages.

I've noticed that problem on a bunch of `xcb_get_*` pages, but it could 
be happening elsewhere too. I checked some at random and none of them 
render properly.

This problem persisted for a couple months, or possibly longer, I 
noticed it it back in April of this year, but it doesn't seem that those 
pages are updated that often, so I could assume it could've been 
happening for much much longer.

Affected pages: I believe anything under 
https://www.x.org/releases/current/doc/man/man3/*.xhtml, but some 
examples include 
https://www.x.org/releases/current/doc/man/man3/xcb_get_font_path.3.xhtml, 
https://www.x.org/releases/current/doc/man/man3/xcb_get_window_attributes.3.xhtml 
and https://www.x.org/releases/current/doc/man/man3/xcb_query_tree.3.xhtml

I hope it will be resolved in near future, but in the meantime, I'll 
just stick to manpage viewer on my system.

I also mentioned that issue on Fediverse, but my instance has strict 
authentication rules, so post is not visible. Should be visible from 
[@]XOrgFoundation[@]floss.social account though!