bug#24755: 25.1; Selection continues with no mouse button pressed

[Mats Palmgren]

1. Visit a buffer with some text
2. Press the left mouse button
3. Drag the mouse to select some text
4. Press the Control key
5. Release the mouse button
6. Continue to move the mouse

Actual Result:
Moving the mouse continues to select text, even though no mouse button
or keys are pressed.

Expected Result:
Selection should stop at 5.

Unfortunately, it's fairly common for me to do 4 before 5 (in
preparation for deleting the selection with C-w for example) so
version 25 is unusable for me with this bug.  This is a new
behavior in v25, it's not present in v23 or earlier versions
that I've used.

In GNU Emacs 25.1.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:     Ubuntu 16.04.1 LTS


Thanks,
Mats