[gps_sirf] Added gps sirf
[ardrone_ins] Fixed a little bug that prevented a succesfull build
[ardrone-sdk] Fixed build error after merge by adding stabilization_attitude_rc_setpoint.c to ap sources in the makefile to get a succesfull build
[gps] fix and cleanup sirf

Actually make it compile:
- replace cpu_time_ticks by sys_time.nb_sec_rem
- only use print function if DEBUG_SIRF

- cleanup indentation
- remove dead/commented code
- add default switch case
- some doxygen comments
Merge branch 'gps_sirf' into ardrone_to_master

Conflicts:
	sw/airborne/subsystems/gps/gps_sirf.c
	sw/airborne/subsystems/gps/gps_sirf.h
[stabilization] Added stabilization_none, this is usefull for the ardrone-sdk version which runs next to the ArdroneLib API program that controls the aircraft so that stabilization is allready done
Merge remote-tracking branch 'origin/stabilization_none' into ardrone_to_master
[stabilization] Changed none to passthrough to avoid confusion with stabilization_none, which also exists. Added a little description also
Merge branch 'stabilization_none' into ardrone_to_master
[ardrone-sdk] Using stabilization passtrough (renamed from none)
[stabilziation] Adjusted makefile to include passtrough and rc_setpoint
Merge branch 'stabilization_none' into ardrone_to_master