device-manager-xi2: Don't divide by the scale factor twice

The coordinates we pass into translate_axes are already scaled.
device-manager-xi2: Clamp coordinates of events to the stage coordinates

The X server can sometimes send us coordinates in the negatives or above
our window in extreme cases. Ensure that the user never sees this.
Remove use of XFixes for showing/hiding the cursor

XFixesShowCursor / XFixesHideCursor does not actually take the suppled
window argument into account -- the effect is actually global. Use
XDefineCursor instead.

https://bugzilla.gnome.org/show_bug.cgi?id=707071