Don't overflow item refcount on get

Counts as a miss if the refcount is too high. ASCII multigets are the only
time refcounts can be held for so long.

doing a dirty read of refcount. is aligned.

trying to avoid adding an extra refcount branch for all calls of item_get due
to performance. might be able to move it in there after logging refactoring
simplifies some of the branches.
static void clock_handler(const int fd, const short which, void *arg) {
    struct timeval t = {.tv_sec = 1, .tv_usec = 0};
    static bool initialized = false;
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    static bool monotonic = false;
    static time_t monotonic_start;
#endif

    if (initialized) {
        /* only delete the event if it's actually there. */
        evtimer_del(&clockevent);
    } else {
        initialized = true;
        /* process_started is initialized to time() - 2. We initialize to 1 so
         * flush_all won't underflow during tests. */
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
        struct timespec ts;
        if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
            monotonic = true;
            monotonic_start = ts.tv_sec - ITEM_UPDATE_INTERVAL - 2;
        }
#endif
    }

    evtimer_set(&clockevent, clock_handler, 0);
    event_base_set(main_base, &clockevent);
    evtimer_add(&clockevent, &t);

#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    if (monotonic) {
        struct timespec ts;
        if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
            return;
        current_time = (rel_time_t) (ts.tv_sec - monotonic_start);
        return;
    }
#endif
    {
        struct timeval tv;
        gettimeofday(&tv, NULL);
        current_time = (rel_time_t) (tv.tv_sec - process_started);
    }
}

static void clock_handler(const int fd, const short which, void *arg) {
    struct timeval t = {.tv_sec = 1, .tv_usec = 0};
    static bool initialized = false;
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    static bool monotonic = false;
    static time_t monotonic_start;
#endif

    if (initialized) {
        /* only delete the event if it's actually there. */
        evtimer_del(&clockevent);
    } else {
        initialized = true;
        /* process_started is initialized to time() - 2. We initialize to 1 so
         * flush_all won't underflow during tests. */
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
        struct timespec ts;
        if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
            monotonic = true;
            monotonic_start = ts.tv_sec - ITEM_UPDATE_INTERVAL - 2;
        }
#endif
    }

    evtimer_set(&clockevent, clock_handler, 0);
    event_base_set(main_base, &clockevent);
    evtimer_add(&clockevent, &t);

#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
    if (monotonic) {
        struct timespec ts;
        if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
            return;
        current_time = (rel_time_t) (ts.tv_sec - monotonic_start);
        return;
    }
#endif
    {
        struct timeval tv;
        gettimeofday(&tv, NULL);
        current_time = (rel_time_t) (tv.tv_sec - process_started);
    }
}
