bug#23179: 25.0.92; Restore `M-,' to continue etags search

[Anders Lindgren]

Why is showing the UI a problem?  You can always delete the window if
you don't want to see it.  "C-x 0" is all it takes.

 I use a number of side-by-side windows, each typically contains one thing I'm working on. If I do a search in one window, I don't want the content of another to be obscured. C-x 0 is out of the question, as it would break the side-by-side window layout.

    -- Anders