Make tasklist order reflects real window position

[zhangkun83]

Switching window operations are based on the order that windows appear on the tasklist, which can be different from their real positions. Sometimes it becomes confusing.

Instead of allowing tasklist order to be manually manipulated, I'd like to bind it with the real window position. For window A and B, B should be to the right of A on the tasklist if,

1. If B.x > A.x, or
2. If B.x == A.x and B.y > A.y