[mdspan.layout] Remove stray \tcode.

[Eelis]

I threw in a couple of other \tcode fixes for things that weren't rendering wrong but were still unconventional (and cxxdraft-htmlgen doesn't handle \tcode V).

[eisenwave]

The diff looks good, but ideally, the commits would have proper section labels. The changes aren't all in [mdspan.layout].

[Eelis]

The diff looks good, but ideally, the commits would have proper section labels. The changes aren't all in [mdspan.layout].

I struggle to think of a good way to add a description of these insignificant drive-by fixes in other sections into the commit title.

[tkoeppe]

Great finds, thanks!