bug#18939: 24.4; middle-click sometimes pastes data other than the PRIMARY selection

[Glenn Morris]

Stefan Monnier wrote:

> I haven't tried with another Emacs process, but I did try with an xterm
> and got the same result.

Totally reproducible for me in emacs-24 or Debian's 24, but curiously
not apparently in master... If someone else sees the same, they might
try bisecting to find what fixed it. There does seem to be weirdness in
that some times it does _not_ happen even with 24. I think maybe I
convinced myself this was due to selecting Emacs by clicking on the
window border rather than in the actual body of scratch. But that could
be coincidence I suppose.

in xterm:
emacs -Q
M-< C-k        # in scratch
mouse-1 on xterm that launched Emacs, double mouse-1 on "emacs"
mouse-1        # in scratch. NB in the buffer, not eg on the WM frame
mouse-2
  -> ";; This buffer is for notes..."

This is under XFCE on Debian testing, in case that matters, with
WM focus-follows-click.