added logging for mrn_hash_remove().
added logging for mrn_hash_remove().

yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga,naoa/mroonga,mroonga/mroonga,mroonga/mroonga,naoa/mroonga,mroonga/mroonga,naoa/mroonga,yoku0825/mroonga,yoku0825/mroonga,yoku0825/mroonga