px4io: configure APM use of px4io without RC handling
APM: configure px4io for no RC handling and no mavlink pipe
added libtomcrypt library
added libtomfastmath
added auth command
ms5611: enabled debug()
mpu6000: added logging of good transfers and enable debug

this helps tracking down a startup issue
Revert "Cranking up bus speeds for all sensors to achievable 10.4 MHz, will cut the bus lock time to half"

This reverts commit d14360f5b513b7d5b591672f7bb1297fd4704a44.

This was found to be unreliable on one 2.4 board, so is too high risk
for release without understanding the issue
ms5611: added "ms5611 test2"

this reports sudden changes in D1, useful for diagnosing temperature
related issues
px4io: support PX4IO_P_SETUP_FORCE_SAFETY_OFF

this allows the FMU to force the safety off on the IO board. Useful in
two cases:

 1) vehicles where the safety switch is impractical or not useful
 (eg. HAB planes or internal combustion motors)

 2) doing ESC calibration on multi-copters
pwm: added PWM_SERVO_SET_FORCE_SAFETY_OFF ioctl

this allows the safety switch on px4io to be forced off
uORB: added an ORB topic for system_power

holds power supply state and 5V rail voltage on FMUv2
adc: publish system_power ORB topic from ADC
meas_airspeed: correct MS4525 airspeed using 5V rail voltage

the slope seems to be reasonably consistent between sensors
meas_airspeed: added temperature compensation with voltage too
airspeed: cope properly with reversed tubes on pitot tube

report both a raw (signed) and non-raw (unsigned) differential
pressure. The signed value needs to be used for calibration to prevent
a bias at low airpeeds if the tubes are reversed
hmc5883: properly reset mag to normal state on calibration fail

and add current output in "hmc5883 info"
board_serial: use a uint8_t buffer

we should not be using 'char' for binary APIs, as the C standard does
not specify if it is signed or unsigned, so results may not be
consistent
auth: use get_board_serial() interface
tests: disable mathlib tests for APM

APM does not link in mathlib