Merge remote-tracking branch 'contiki/master' into develop

Conflicts:
	core/net/mac/contikimac/contikimac.c
	platform/avr-ravenusb/Makefile.avr-ravenusb
	platform/exp5438/Makefile.exp5438
	platform/micaz/Makefile.micaz
	platform/native/Makefile.native
	platform/sky/Makefile.common
	platform/sky/Makefile.sky
	platform/wismote/Makefile.wismote
	platform/z1/Makefile.common
	platform/z1/Makefile.z1
	tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/Msp802154Radio.java