Fix CursorMove command to correctly honour EdgeScroll settings.

Fix CursorMove command to correctly honour EdgeScroll settings.

Rework the logic of how the CursorMove command works with different
EdgeScroll settings.  Don't try and move the cursor back, as paging may well
have already taken place, rendering the code useless anyway.

Instead, check to see if the cursor is in a pan-window at either edge
(assuming EdgeScroll is disabled), and if its next move would cause a page
scroll, to simply never move the cursor at all.