drag.slider/drag.xyslider cursor value at "end" isn't correct

For some reason cursor value does not get derived correctly at "end" handler. It seems pageX and clientX values are incorrect in this case.

Perhaps a possible workaround would be to pass last known good value from move or begin to end.

Start by reproducing the issue in drag.slider and drag.xyslider, focusing on the end handler and comparing its pageX and clientX values with those from move or begin. Done means the cursor value is derived correctly when the drag ends, including at the end position.

Written by the indexing model from the issue text.