bug#52126: Problematic characters in info node names

[Kyle Meyer <kyle@kyleam.com>]

Glenn Morris writes:

> Stefan Kangas wrote:
>
>> Did something change here since the above note in admin/release-process
>> was written in 2013 (commit 16bcc96df4)?
>
> Yes. It's easy to find old versions of the Texinfo manual, eg
> http://www.nongnu.org/texi2latex/texinfo/Node-Line-Requirements.html
>
> Newer Texinfo is less strict, but Emacs configure still claims to
> support 4.13.

I wonder whether 4.13 actually has a problem with the cases flagged in
this issue, where the parentheses are not at the start of the text.
Texinfo's ab404029d0 (parens only disallowed when looks like an external
manual ref, 2011-09-18) made the following text change:

   @cindex Characters, invalid in node name
   @cindex Invalid characters in node names
   @cindex Node names, invalid characters in
  -Unfortunately, you cannot use periods, commas, colons or parentheses
  -within a node name; these confuse the Texinfo processors.  Perhaps
  -this limitation will be removed some day, too.
  +Unfortunately, you cannot use periods, commas, or colons within a node
  +name; these confuse the Texinfo processors.  Also, a node name may not
  +start with a left parenthesis and contain a right parenthesis, as in
  +@code{(not)allowed}; this specifies an external manual in Info.
  +Perhaps these limitations will be removed some day, too.

That looks to be a pure documentation update to more accurately describe
the restrictions.  The commit message links to a thread [*] that seems
to confirm that.  There Patrice Dumas says

  What is not allowed, in reality, and leads to an error message is parentheses
  beginning at the beginning of the node name as you said:
  
   @node (man)bad
  
   c.texi:6: Syntax for an external node used for `(man)bad'

[*] https://lists.gnu.org/archive/html/bug-texinfo/2011-09/msg00024.html