Fix compile errors
ArduPPM: throttle failsafe is now triggered on single channel loss but recovery from the throttle low is possible
ArduPPM: added a define for throttle low fail-safe indication
ArduPPM: changes for throttle low indication and also recovery after a throttle low indication are now set with defines
ArduPPM: latest changes are now disabled by default, throttle low triggering by single channel errors and also recovering from a throttle low event can be enabled with defines
Merge pull request #6 from julianoes/ppm_encoder_fixes

ArduPPM

Two new defines added:

_THROTTLE_LOW_FAILSAFE_INDICATION: Throttle low indication and thus APM fail-safe triggering when a single channel error is detected.

_THROTTLE_LOW_RECOVERY_POSSIBLE: Throttle low is reset when a disconnected channel comes back and full control regained.
AP_Scheduler: added new scheduler library

this will be used for main loop control
Copter: use new AP_Scheduler library
Copter: only print perf data when SCHED_DEBUG is non-zero
AP_Scheduler: expose debug variable
AP_Scheduler: show scheduler task slips

this is when a task doesn't run at the desired rate
AP_GPS: initialise _step to zero in all drivers

new() does not zero-fill memory
DataFlash: added block based dataflash writes

these are about 10x faster than the old writes
DataFlash: update for new block API
Copter: use the new logging methods for 2 packet types

the rest still need to be converted
ArduCopter: reduce redundant event logging

We now only write state changes to the dataflash log when they have
changed.
Also replaced <tab> with <space> in AP_State.pde
ArduCopter: fixed minor bug in logging of parameter changes to dataflash

It is questionable whether we should even bother writing these to the
dataflash as there is no way to recognise which parameter has been
affectded
ArduCopter: use new logging method for remaining packet types

Additional changes include renaming RAW dataflash type to IMU
DataFlash Empty: conform to blockread/write virtual if
AP_HAL_SMACCM: add LICENSE file