Support new subsections (at least, 3type, 2type, and 3const)

[alejandro-colomar]

Describe the bug

The Linux man-pages project is adding new subsections: at least 3type, 2type, and 3const. Maybe also 3head and 2head.

That would mean adding directories such as man3type, and file extensions such as .3type.

Autocomplete for those sections is not working currently. Maybe an approach could be to allow arbitrary subsections. If not, another approach would be to support those specific subsections.

To reproduce

Install the Linux man-pages from source (sudo make install) from the current git HEAD, then

man -s 3type [TAB] should show only a bunch of options, since there are only a few dozens of pages in that subsection. Instead, it shows that there are 9k+ possibilities, since it doesn't understand the subsection 3type.

Versions (please complete the following information)

• [x] Operating system name/distribution and version: Debian Sid
• [x] bash version: 5.1.16(1)-release
• [x] bash-completion version: 2.11