Based on evdev's similar properties, including using the name "middle"
button, to avoid confusion with evdev's 3rd button emulation for
emulating the right button on a single button mouse.
Allows manual enable & disable at runtime.
Exports new xf86-mouse.pc & xf86-mouse-properties.h for property name
definitions.
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Alexandr Shadchin <alexandr.shadchin@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
