check index at increments crawlerstats_t->histo
check index at increments crawlerstats_t->histo

Very rarely, current_time will be greater than expiration time of item.
If an item has expired at after check its expiration in crawler thread,
access to crawlerstats_t->histo with invalid index. so segmentation
fault occurs as a result of access violation.

gencer/memcached,gencer/memcached,memcached/memcached,elfchief/memcached,dormando/memcached,guikcd/memcached,memcached/memcached,elfchief/memcached,elfchief/memcached,gencer/memcached,elfchief/memcached,memcached/memcached,guikcd/memcached,memcached/memcached,guikcd/memcached,guikcd/memcached,dormando/memcached,dormando/memcached,guikcd/memcached,gencer/memcached,dormando/memcached,gencer/memcached,elfchief/memcached,memcached/memcached,dormando/memcached