[ahrs] gx3 minor fixes

closes #565
[stabilization] float_euler fixes so it actually compiles
[rotorcraft] quat_float: rename x_sum_err_eulers to x_sum_err
[telemetry] fix INS_Z
[fixedwing] add PERIODIC_SEND_AHRS_QUAT_INT
[fixedwing] remove sys_time include from autopilot.h
[test] update compare_ahrs
Merge branch 'master' of https://github.com/podhrmic/paparazzi