I discovered some warnings...especially the last one seems to be a real problem

hwtimer_cpu.c:243:55: warning: unused parameter 'fcpu' [-Wunused-parameter]
void hwtimer_arch_init(void (*handler)(int), uint32_t fcpu)

irq_cpu.c:295:43: warning: unused parameter 'info' [-Wunused-parameter]
void native_isr_entry(int sig, siginfo_t *info, void *context)

[removed one warning (was not in master]

mutex.c:94:46: warning: unused parameter 'yield' [-Wunused-parameter]
void mutex_unlock(struct mutex_t *mutex, int yield)

vtimer.c:80:24: warning: unused parameter 'ptr' [-Wunused-parameter]
void vtimer_tick(void *ptr)

vtimer.c:112:28: warning: unused parameter 'ptr' [-Wunused-parameter]
void vtimer_callback(void *ptr)