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

we should be able to do 400Hz in future

use a time base sample wait, with 1kHz sampling

usleep can cause a large delay with PREEMPT kernel

this fixes the Replay tool

this will make it easier for other boards (such as NAVIO) to implement
their own RCInput mechanism