(cua--rectangle-set-corners): Ensure that

(cua--rectangle-set-corners): Ensure that
point is set (and displayed) inside rectangle.
(cua--rectangle-operation): Fix for highlight of empty lines.
(cua--highlight-rectangle): Fix highlight for tabs.
Position cursor at left/right edge of rectangle using new `cursor'
property on overlay strings.
(cua--indent-rectangle): Don't tabify.
(cua-rotate-rectangle): Ignore that point has moved.