test for race condition in hwtimer_spin
INCLUDES, add chronos board

set INCLUDES according to the transceiver being used
Merge pull request #55 from LudwigOrtmann/test_hwtimer_spin

test for race condition in hwtimer_spin
Merge pull request #56 from LudwigOrtmann/default-update

INCLUDES, add chronos board
add valgrind option to Makefile
Merge pull request #58 from mehlis/vg-makefile

add valgrind option to Makefile