bug#25936: Fix for whitespace.el to make it read tab-width and indent-tabs-mode correctly

[npostavs]

Reuben Thomas <rrt@sc3d.org> writes:

> However, on further investigation, I can't see why these local variables
> are needed. Currently, whitespace-mode makes buffer-local copies of
> indent-tabs-mode and tab-width, with names prefixed by "whitespace-". But
> these variables are buffer-local if necessary already, and whitespace-mode
> never tries to change them.

These variables seem to have been introduced in [1: 55d1cfe870].  I
agree that it looks like there is no need for them, but I'll wait
another couple weeks in case someone else has some insights.  Adding
author of that commit (and the person mentioned as "suggesting" it) on
CC in case they might remember anything about it.

1: 2008-04-16 03:41:17 +0000 55d1cfe8703c5829bacc8d129277f1f9b33950f6
  Honor the indent-tabs-mode and tab-width setting from user.