Fixed an issue where an aggregate with millions of child buckets gets very slow.
Fixed an issue where an aggregate with millions of
child buckets gets very slow.

* buckets/aggregate_buckets.c
  (aggregate_context_t): Keep a pointer to last bucket in
   the list.
  (serf_bucket_aggregate_become,
   serf_aggregate_restore_snapshot): Initiate 'last' ptr.
  (serf_bucket_aggregate_append): Use the 'last' ptr to 
   append at the end of the list, 

sworda/serf,x-clone/serf,krime/serf,blueszhangsh/serf,stoneCC/serf,muthusuba/serf,google-code-export/serf,zhupan/serf,KyleSanderson/serf,liuzongquan/serf,idomon/serf,soufianeEL/serf,TommyU/serf,SirJson/serf,KyleSanderson/serf,SirJson/serf,pengdu/serf,wzugang/serf,lazysoez/serf,pengdu/serf,justinweb/serf,wzugang/serf,wzugang/serf,x-clone/serf,krime/serf,pengdu/serf,blueszhangsh/serf,liuzongquan/serf,muthusuba/serf,zhupan/serf,yesoce/serf,idomon/serf,soufianeEL/serf,KyleSanderson/serf,justinweb/serf,blueszhangsh/serf,Manouchehri/serf,Manouchehri/serf,zhengcq315/serf,krime/serf,SirJson/serf,yesoce/serf,x-clone/serf,KyleSanderson/serf,alex1818/serf,blueszhangsh/serf,krime/serf,justinweb/serf,alex1818/serf,soufianeEL/serf,TommyU/serf,lazysoez/serf,stoneCC/serf,alex1818/serf,stoneCC/serf,zhengcq315/serf,zhengcq315/serf,zhupan/serf,zhengcq315/serf,Manouchehri/serf,idomon/serf,idomon/serf,pengdu/serf,Manouchehri/serf,liuzongquan/serf,google-code-export/serf,google-code-export/serf,x-clone/serf,muthusuba/serf,sworda/serf,soufianeEL/serf,TommyU/serf,google-code-export/serf,sworda/serf,sworda/serf,TommyU/serf,lazysoez/serf,muthusuba/serf,wzugang/serf,yesoce/serf,alex1818/serf,stoneCC/serf,zhupan/serf,SirJson/serf,liuzongquan/serf,yesoce/serf,justinweb/serf,lazysoez/serf