Merge pull request #1575 from Kijewski/use-sched_active_pid

boards/avsextrem/drivers/avsextrem-smb380.c

core/include/thread.h

core/sched.c

core/thread.c

cpu/arm_common/syscalls.c

cpu/lpc1768/syscalls.c

cpu/nrf51822/syscalls.c

cpu/sam3x8e/syscalls.c

cpu/stm32f0/syscalls.c

cpu/stm32f3/syscalls.c

cpu/stm32f4/syscalls.c

drivers/cc110x/cc1100_phy.c

sys/posix/pthread/pthread_barrier.c

sys/posix/pthread/pthread_cond.c

sys/posix/pthread/pthread_rwlock.c