Merge pull request #648 from atiselsts/contrib/cc13xx-tsch

arch/cpu/cc26xx-cc13xx/Makefile.cc13xx

arch/cpu/cc26xx-cc13xx/cc13xx-cc26xx-def.h

arch/cpu/cc26xx-cc13xx/rf-core/ble-hal/ble-hal-cc26xx.c

arch/cpu/cc26xx-cc13xx/rf-core/cc13xx-50kbps-tsch.c

arch/cpu/cc26xx-cc13xx/rf-core/cc13xx-50kbps-tsch.h

arch/cpu/cc26xx-cc13xx/rf-core/ieee-mode.c

arch/cpu/cc26xx-cc13xx/rf-core/prop-mode.c

arch/cpu/cc26xx-cc13xx/rf-core/rf-core.c

arch/cpu/cc26xx-cc13xx/rf-core/rf-core.h

arch/cpu/cc26xx-cc13xx/ti-lib.h

examples/6tisch/6p-packet/Makefile

examples/6tisch/etsi-plugtest-2017/Makefile

examples/6tisch/simple-node/Makefile

examples/6tisch/sixtop/Makefile

os/net/mac/tsch/tsch-const.h