fix use of math lib in rotorcraft_cam module
[telemetry] replace old downlink macros with functions

- update messages generator
- generic device with uart support
- initial support of pprz protocol (transparant)
- fix types in downlink variables
[telemetry] cleaning downlink header
[telemetry] convert xbee to new downlink functions
[telemetry] start conversion of pprzlog transport
[telemetry] convert w5100 to new format

- actually, w5100 is only a device using pprz protocol
- compiling but not tested
- very strange manipulation of pointers in w5100_receive and
  w5100_read_data functions
- I doubt this is actually still working...
[telemetry] converting superbitrf to generic device API
[sdlog] fix sdlog and extra datalink
[udp] convert udp to generic device API
[usb_serial] convert usb_serial to generic device API
[telemetry] change register callback to pass arguments
[telemetry] convert macros in registered callback to functions
[telemetry] add support for ivy_transport
[telemetry] fixing and cleaning a few stuff
last minute fix
fix some bug reported by TravisCI
missing parenthesis
more bug fix
Merge remote-tracking branch 'paparazzi/master' into datalink_functions

Conflicts:
	sw/airborne/subsystems/gps.c
[test] update compile_all_aircrafts test

Also replace LOCAL_CFLAGS (which wasn't used anymore) with USER_CFLAGS (and add where missing).
Now you can e.g. test compile all aircrafts/targets in your conf and add extra flags like treating warnings as errors:

$ J=AUTO USER_CFLAGS=-Werror prove conf/examples