Limit integral windup, some new PID values and linearise thrust.

thrust.c

@@ -0,0 +1,15 @@
+/* thrust.c */
+
+#include "fisqrt.h"
+#include "timer.h"
+
+float linearise_thrust(float x)
+{
+	return fisqrt(fisqrt(x*x*x));
+}
+
+void set_thrust(int motor, float x)
+{
+	timer_set_pwm_value(motor, (int)(linearise_thrust(x) * PWM_MAX));
+}
+