Merge pull request #1440 from Kijewski/issue-1436

core/hwtimer.c

core/include/mutex.h

core/include/queue.h

core/mutex.c

drivers/cc110x/cc1100_phy.c

drivers/sht11/sht11.c

sys/net/network_layer/sixlowpan/lowpan.c

sys/net/routing/etx_beaconing.c

sys/net/routing/rpl/rpl.c

sys/vtimer/vtimer.c

tests/test_mutex_unlock_and_sleep/main.c

tests/test_pthread_condition_variable/main.c

tests/test_thread_cooperation/main.c