Make idle.c more portable:     type of active_worker_count changed to uintptr_t
Make idle.c more portable:
    type of active_worker_count changed to uintptr_t

    atomic_add_i64 changed to generic atomic_add

HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit