bug#30068: 26.0; REGRESSION: no doc for `x-display-pixel-*'

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: 30068@debbugs.gnu.org
> Date: Thu, 11 Jan 2018 14:26:02 -0500
> 
> Keep the real doc only in xfns.c, makes the others just say <skip>, or
> <see:xfns.c>, and change Fsnarf_documentation to respect <skip>.

Sounds fine.  Are there any downsides?

> Related: I see Fsnarf_documentation already has skip_file, but it
> doesn't handle lisp files. Maybe it could be taught about
> preloaded-file-list, which would have avoided this particular problem.

Not sure how: pc-win.el is preloaded (on some platforms).  Or maybe I
misunderstand you.