This patch adds mouse cursors to the joystick scrolling feature.
On Tiberian Sun, which itself had joystick scrolling, the same cursors are
used as in the original game.
As the older games did not have joystick scrolling, I've had to make a
best-effort guess as to what were suitable cursors.
-> When scrolling in all directions is available, the default arrow
cursor is used.
-> When a direction is blocked, the edge-scrolling blocked direction
cursor is used.
