Higher-res gyro readings to reduce rounding errors.

Doesn't actually seem to help much but also doesn't cost much so
stay with the higher precision version.
Use 3 pins to drive 30 LEDs each, clock out pixels in parallel.

Instead of having to clock out 90 values through one pin for 2.7ms, use
3 pins (PC0, PC1, PC2 or Analog 1, 2, 3) each connected to two 15-LED
strips, so we can simultanouesly output to 3 streams of values and only
need 0.9ms.

The half-wheel program now gets 677 fps instead of 303, the text program
397 instead of 231 fps.