[LyX/master] Fix backspace deletion of selected items with change tracking

[Jean-Marc Lasgouttes]

Le 13/01/2020 à 17:45, Jürgen Spitzmüller a écrit :
> Am Montag, den 13.01.2020, 16:14 +0100 schrieb Jean-Marc Lasgouttes:
>> Yes, but you do not know what column was added.
> 
> This is how it was before as well. We could color the lines of the
> added/removed columns/rows blue or red.

To put things differently: what does the support for tracking row/column 
addition/removal that you added does in terms of functionality?

JMarc