`size-indication-mode' tweak

[Drew Adams]

After the release:

How about considering this minor tweak to `size-indication-mode'?
The doc string would also need to be updated accordingly.

The idea is this: Whenever the region is active in transient-mark mode, the
size indication shows the size of the region, not the size of the buffer.

The implementation change is trivial - just use this for the
`size-indication-mode' part of `mode-line-position':

(size-indication-mode
 (8 ,(propertize
      (if (and transient-mark-mode mark-active)
          (format " %d chars" (abs (- (mark t) (point))))
        " of %I")
      'face (and transient-mark-mode mark-active 'region)
      'help-echo help-echo)))

where help-echo is bound as usual.

FYI - This library does that, as well as highlighting the column number when
the current column is greater than a given limit (option):
(http://www.emacswiki.org/cgi-bin/wiki/modeline-posn.el)