PROBLEM:
libinput ignores settings done by "xinput set-button-map" that set wheels to zero to deactivate them.

For details, please see: http://forums.debian.net/viewtopic.php?f=6&t=137104
Bug https://bugs.freedesktop.org/show_bug.cgi?id=104960 is possibly also influenced by this issue.

CAUSE:
My investigation showed what causes the bug.
The problem is in libinput.c.
Please look at the comments added by me to understand the problem.

SOLUTION:
My quick fix factually just consisted of disabling the wheel by always returning zero movement.
A *proper* fix would check whether the wheel is enabled at all in the button map set by xinput or xorg.conf, and discard the events if wheel is disabled.

<<<CODE SNIPPET START>>>
LIBINPUT_EXPORT double
libinput_event_pointer_get_axis_value_discrete(struct libinput_event_pointer *event,
					       enum libinput_pointer_axis axis)
{
	struct libinput *libinput = event->base.device->seat->libinput;
	double value = 0;

	require_event_type(libinput_event_get_context(&event->base),
			   event->base.type,
			   0.0,
			   LIBINPUT_EVENT_POINTER_AXIS);

	if (!libinput_event_pointer_has_axis(event, axis)) {
		log_bug_client(libinput, "value requested for unset axis\n");
	} else {
		switch (axis) {
		case LIBINPUT_POINTER_AXIS_SCROLL_HORIZONTAL:
			value = event->discrete.x;
			break;
		case LIBINPUT_POINTER_AXIS_SCROLL_VERTICAL:
			value = event->discrete.y;
			break;
		}
	}
// 	return value;
// 	
// 	YUCKY BUG HERE: xinput-disabled wheels will generate events
// 	FIX by checking xinput button map
// 	for now just FSCK THE SCROLL SH!T
		
	return 0;
}

LIBINPUT_EXPORT enum libinput_pointer_axis_source
libinput_event_pointer_get_axis_source(struct libinput_event_pointer *event)
{
	require_event_type(libinput_event_get_context(&event->base),
			   event->base.type,
			   0,
			   LIBINPUT_EVENT_POINTER_AXIS);

// 	return event->source;
// 	
// 	YUCKY BUG HERE: xinput-disabled wheels will generate events
// 	FIX by checking xinput button map
// 	for now just FSCK THE SCROLL SH!T
	
	return 0;
}
<<<CODE SNIPPET END>>>