InertialNav: fix for get_velocity_xy

forgot to sq
Copter: updated toy gains
TradHeli: Change default Auto-Yaw to Yaw Look Ahead

This leads to smoother flight in Auto modes, particularly with fast waypoints.
TradHeli: Change user description for COLYAW parameter.
Copter: formatting fix to config.h
AP_Notify: make APM2 ToshibaLED driver more efficient

use one I2C transfer, not 3
AP_AHRS: prevent GPS yaw resets on compass errors

when we switch from compass heading to GPS heading we don't want to
trigger a sudden GPS yaw reset
AP_AHRS: fixed wrapping bug in GPS based heading error

this bug could cause the GPS based yaw to use an expensive reset far
too often
AP_AHRS: removed vertical G limit on GPS velocity correction

this limit could lead to a bias in the accel drift correction, and is
frequenctly exceeded
AP_AHRS: removed limit on normalisation of accel reference vectors

this could lead to a bias in the accel drift correction
AP_AHRS: save memory and reduce pointer references

use a refence for ins, and don't save gyro and accel between updates
AC_Fence: update for AHRS API changes
AP_YawController: update for AHRS API change
DataFlash: use const ins reference

save some pointer dereferences
AP_TECS: update for AHRS API change
AP_InertialSensor: use const reference returns

saves some vector copies
AP_InertialNav: update for AHRS API changes
VARTest: update for AHRS API change
Plane: update for API changes
Copter: update for AHRS API changes