this saves a tiny amount of time by removing the memory copy of a
Vector3f

fixes pull #1320

thanks Arthur!

this is the start of multi-core aware code

this avoids suspending timers when transferring data between main
thread and SPI read thread

reference to rc_1, rc2 are replaced with constant updates during
acro_run

TradHeli: Add pointer for pilot roll/pitch inputs to attitude_control constructor. To be used for flybar passthrough.

AC_AttitudeControl_Heli: Create Flybar Passthrough flag which will be used for control pass-through.

the EKF check works reliably but attempts to check the inertial nav for
errors has not been successful.  I could not find a way to reliably
catch flyaways without also introducing false positives (and thus
unwanted LANDings)

use a single time base in all code

this can be used for much simpler scheduling, without any wrap
handling

setup the timer start after we've started the conversion to prevent
reading faster than the MS5611 is able to produce values

this avoids drift in the 1kHz timer, to avoid bias in the IMU
filtering

when running off a 1kHz timer and reading at 1kHz it is better to
double sample than it is to skip a sample, as skipping samples will
throw the filter off, whereas a double sample will have minimal effect