High CPU usage when doing camera orbit.

[Bram]

The high CPU rate is unrelated to the mouse polling rate, I have determined.

I changed my razor mouse to poll at 125Hz instead of 1000Hz, with the following results:

• The mouse stutter is gone!
• The CPU usage by beam.smp is still very high as soon as you move the mouse, regardless whether the polling rate is 125 or 1000. Just the fact that you generate mouse events makes the CPU usage go high.