[stm32] removed -mapcs-32 assembler option, as it doesn't exist anymore since gcc 4
[build system] more makefile cleanup for lpc stuff
- removed usb_lib target, not used anywhere
- fix lpc bootloader makefile
[boards] readability and overwritable defaults
[v4.2-import] Recent additions to V4.2
remove some unnecessary checks from setup_actuators
[sim] really add launchsitl as symlink to pprzsim-lauch for backwards compat
Merge pull request #360 from paparazzi/recent_addition_to_v4.2

minor updates from stable v4.2