branch mw4: pull in roll changes to servoMix.c, and rollCntrl.c from _mw4fbw: SILsim stabilize mode working very well, auto mode roll gain looks too low
branch mw4: clean up SILsim options.h: SILsim auto mode working very well
branch mw4: fix some issues with Xplane plugin: SILsim had broken, looks like disagreement between Xplane pitch and IMU pitch