[PATCH] docs: pdfdocs: Prevent column squeezing by tabulary

Setting a reasonable width to \tymin prevents column squeezing
by tabulary.
Width of 20em works well in almost all the tables still in the
ascii-art format.

Excerpt from tabulary package documentation at [1]:

    To stop very narrow columns being too 'squeezed' by this process
    any columns that are narrower than \tymin are set to their natural
    width.

[1]: https://mirrors.ctan.org/macros/latex/contrib/tabulary/tabulary.pdf

Note: Sphinx has its own default value of \tymin set in
sphinxlatextables.sty (Sphinx 4.0.2) and sphinxmulticell.sty
(Sphinx 2.4.4) as follows:

    \setlength{\tymin}{3\fontcharwd\font`0 }

, which is not sufficient for kernel-doc.

Tested against Sphinx versions 2.4.4 and 4.0.2.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
---
Hi all,

This is another attempt to improve pdfdocs output.
As far as I see, I don't see any obvious regression by
this change.

The effect of this change can be seen in (not limited to)
the MODULE_LICENSE section in process.pdf (pages 10 and 11).

I'd like to know this change looks reasonable to you.

Any feedback is welcome!

        Thanks, Akira

--
 Documentation/conf.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/conf.py b/Documentation/conf.py
index 25aa00c707b0..a05225056e08 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py

@@ -353,6 +353,8 @@ latex_elements = {
 
     # Additional stuff for the LaTeX preamble.
     'preamble': '''
+	% Prevent column squeezing of tabulary.
+	\\setlength{\\tymin}{20em}
         % Use some font with UTF-8 support with XeLaTeX
         \\usepackage{fontspec}
         \\setsansfont{DejaVu Sans}

-- 
2.17.1