cursor: do not clamp motion coordinates for xdg-shell surfaces

cursor: do not clamp motion coordinates for xdg-shell surfaces

...when pointer moves off the xdg-shell surface which is possible when
for example grabbing a scroll-bar or selecting text.

Clamping results in undetected pointer motion when applied in the
direction of movement (for example clamping at view->y masks vertical
movement when the y-coordinate is greater than view->y), which in turn
can appear as sporadic to the end-user.