Copter: add ACRO_EXPO param values
Linux: added example startup script for plane
HAL_Linux: split RCInput class into generic and PRU implementations

this will make it easier for other boards (such as NAVIO) to implement
their own RCInput mechanism
HAL_Linux: split off RCOutput class to be specific to PXF and ERLE

this fixes the Replay tool
HAL_Linux: don't use usleep() in suspend_timer_procs()

usleep can cause a large delay with PREEMPT kernel
AP_InertialSensor: fixed timer bug in HIL sensors
AP_InertialSensor: update MPU9250 driver for 1kHz operation

use a time base sample wait, with 1kHz sampling
Copter: run Linux boards at 100Hz for now

we should be able to do 400Hz in future
AP_InertialSensor: get rid of data_ready for MPU9250

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
HAL_Linux: run timer thread at average 1kHz without drift

this avoids drift in the 1kHz timer, to avoid bias in the IMU
filtering
AP_Baro: prevent reading the MS5611 too fast

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