Stabilization: fix small typo for yaw autotuning

This prevented the yaw gain autoadjusting, but was
always going to the max level.
Sim Posix: use -D USE_POSIX for consitency with OSX
PiOS Semphore: fix for SIM_OSX

Sim has no ISR methods. This maps them to the normal
non-ISR methods for simulation.
all_fw: disable unused FreeRTOS API functions
pios_thread: add
all_fw makefiles: added pios_thread.c
all flight: use pios_thread
all pios_config.h: changed unit of PIOS_EVENTDISPATCHER_STACK_SIZE to bytes
pios_mutex: add missing "" in #error statement
pios_semaphore: add missing "" in #error statement
GenericI2CSensor/i2c_vm: use pios_thread only if PIOS_INCLUDE_FREERTOS is defined
This is not an optimal solution but the cleanest to get the unit test running again.
Ideally a unit test would use the PiOS simulation and thus have access to all os APIs.
tests/i2c_vm: remove simulated FreeRTOS API functions
pios_opahrs: delete as it isn't being used anymore
ManualControl/transmitter_control: fixes timeDifferenceMs()
Merge pull request #1273 from peabody124/stabilization_useless_if

Stabilization: fix small typo for yaw autotuning
Merge pull request #1253 from lilvinz/pios_thread

Pios thread
PiOS CAN: add ability send arbitrary messages

This approach is somewhat hacky, but allows
sending and fetching messages.
PiOS CAN: support sending custom messages

This still requires defining the messages at the level
of the driver. However it provides a fairly clean API
and should extend easily when only a few messages are
used.
PiOS CAN: register queue to receive messages

Create a queue that will receive messages for the
known message IDs. Also makes the receive handler
push data on those queues.
CameraStab: send PIOS_CAN_GIMBAL message on update

This passes to the gimbal the desired attitude (to integer
angles) and the attitude of the flight controller. This
will allow more efficiently controlling the attitude with
POI mode or relaying the setpoint from the transmitter.