Re: Fixing some warnings in emacs-26

[Juanma Barranquero <lekktu@gmail.com>]

> LGTM, thanks.  However, please install those on master, as I'd like to
> minimize changes on the release branch: we will start the pretest of
> Emacs 26.3 soon.

OK

> Instead of the arbitrary value of 20, I'd prefer using sizeof for the
> actual text (which should probably be assigned to a variable, to avoid
> mentioning the same text twice).

Done.

Though I wanted to avoid adding complexity for a string message that's
unlikely to change. Also, addpm.c already contains a few instances of
hardcoded constants:

      /* Ensure there is enough room for "...\GNU Emacs\Emacs.lnk".  */
      if (strlen (start_folder) < (MAX_PATH - 20))

and

      char add_item[MAX_PATH*2 + 100];

etc.