Fix issue 79: destroy the APR allocator, if we create it.
Fix issue 79: destroy the APR allocator, if we create it.

* buckets/allocator.c:
  (serf_bucket_alloc_t): Add 'own_allocator' boolean flag.
  (allocator_cleanup): If we created the associated apr_allocator_t,
    destroy it here.
  (serf_bucket_allocator_create): If we created an apr_allocator_t,
    remember that fact by setting the new 'own_allocator' flag.

Patch by: morlov...@google.com
          cmpilato@red-bean.com

justinweb/serf,krime/serf,Manouchehri/serf,muthusuba/serf,justinweb/serf,Manouchehri/serf,Manouchehri/serf,blueszhangsh/serf,sworda/serf,muthusuba/serf,TommyU/serf,liuzongquan/serf,wzugang/serf,blueszhangsh/serf,krime/serf,TommyU/serf,TommyU/serf,wzugang/serf,sworda/serf,krime/serf,justinweb/serf,idomon/serf,idomon/serf,idomon/serf,idomon/serf,wzugang/serf,justinweb/serf,muthusuba/serf,blueszhangsh/serf,blueszhangsh/serf,liuzongquan/serf,liuzongquan/serf,krime/serf,muthusuba/serf,sworda/serf,liuzongquan/serf,TommyU/serf,sworda/serf,Manouchehri/serf,wzugang/serf