SITL → AP_Common Relation

File in libraries/SITL	Includes file in libraries/AP_Common
SIM_FlightAxis.cpp	missing / fcntl.h
SIM_Gripper_EPM.cpp	AP_Common.h
SIM_JSBSim.cpp	missing / fcntl.h
SIM_last_letter.cpp	missing / fcntl.h
SIM_Vicon.cpp	missing / fcntl.h
SIM_XPlane.cpp	missing / fcntl.h
SITL.cpp	AP_Common.h