Remove irrelevant links from C/C++ descriptions. No effort was made to
replace them when there wasn't already a link to CERT C. This will be
done as part of a separate effort, one day.
When an include is not surrounded by empty lines, its content is inlined
on the same line as the adjacent content. That can lead to broken tags
and other display issues.
This PR fixes all such includes and introduces a validation step that
forbids introducing the same problem again.
