bug#27122: 26.0.50; [PATCH] Add customizable to display unprintables as hex

[Eli Zaretskii]

> Date: Tue, 30 May 2017 10:16:28 +0200
> From: Vasilij Schneidermann <v.schneidermann@gmail.com>
> Cc: 27122@debbugs.gnu.org
> 
> > OK, please submit the patch with the necessary documentation, and
> > please add a test for the original and the new behavior.
> 
> Where and how should this feature be tested?  I've found
> test/manual/redisplay-testsuite.el for manual testing of xdisp.c
> features, but also test/src/textprop.el for automated testing which
> suggests test/src/xdisp.el might work out.

Yes, I think test/manual/redisplay-testsuite.el is where the
additional tests should go.

> I've fixed the remaining points.

> * src/xdisp.c (get_next_display_element): Dispatch used format string
>   for unprintables based on new display-raw-bytes-as-hex
>   variable
>   (display-raw-bytes-as-hex): New variable
> * doc/emacs/display.texi: Document the new variable

Please end each sentence in the commit log message with a period, and
please mention the bug number there.  Please also add a short log
entry for etc/NEWS.

Thanks.