Differences between mouse selection and scrolling between v23 and v24

[David McKelvie]

Ive noticed a difference between Emacs 23 and version 24
in a way that affects how I work with Emacs and would like to know how
to get the emacs 23 behaviour back in Emacs version 24.

The issue is a difference in how mouse selection and scrolling interact.

Suppose I have a file which is longer than will fit in a window.

In Emacs 23, 

I can select the first three lines of the file, selecting using the mouse
(drag out three lines using left mouse button).

These three line are highlighted in yellow.

Then I scroll the window down to the bottom, again using the mouse and the RHS 
scroll bar.

Then I click at the bottom of the file and then paste the three lines from the 
top
using the middle mouse button.

Only those three lines of text are pasted at he bottom of the file.

In Emacs 24

When I do the same, ie select top three lines and scroll to bottom and
paste using middle button, then I get the whole of the file pasted in
at the bottom, not just the three selected lines.

The same annoying thing happens if I split the frame and have two windows both 
looking at the same file.

Select the top three lines in frame 1 and then moving mouse to frame 2 extends 
the selection
to where the cursor is.

These tests were run on Ubuntu 14.04

Linux 4.2.0-35-generic #40~14.04.1-Ubuntu SMP Fri Mar 18 16:37:35 UTC 2016 
x86_64 x86_64 x86_64 GNU/Linux

With emacs versions
   GNU Emacs 23.4.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.21)
   of 2013-10-25 on allspice, modified by Debian

   GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.10.7)
   of 2014-03-07 on lamiak, modified by Debian

Both versions of emacs were using the same .emacs file.

So, is there some configuration variable I can set that will re-instate the 23 
behaviour in 24?

Thanks, David