[Gpm] repeat and accel

[Alessandro Rubini]

> Alessandro> Who is going to fix it?
> 
> I can do it, it's very easy, but don't blame me when suddenly
> everybody starts complaining how slow their mouse is in X.

You're right. Then, what about limiting the motion to 128 before
passing data to the repeater?

Actually, I can repeat the problem. With msc protocol is not a real
issue, as one packet can report ranges from -256 to 254 (not -128..127
like other protocols).

Actually, this will also catch the case where the original mouse
is MSC and the repeater protocol has less bits for motion.

/alessandro