Make 'mouse-drag-and-drop-region' more robust and customizable

Make 'mouse-drag-and-drop-region' more robust and customizable

* lisp/mouse.el
(mouse-drag-and-drop-region-cut-when-buffers-differ): New option
to permit 'mouse-drag-and-drop-region' to cut text also when source
and destination buffers differ.
(mouse-drag-and-drop-region-show-tooltip): New option to toggle
display of tooltip during mouse dragging on graphic displays.
(mouse-drag-and-drop-region-show-cursor): New option to toggle
moving point with mouse cursor during mouse dragging of region.
(mouse-drag-and-drop-region): New face to highlight original
text while dragging.
(mouse-drag-and-drop-region): Make use of new options and face.
Ignore errors during tracking.