improve dump_allocator, add dump_one_pool

- dump_one_pool dumps the size of a pool not including child pools
- dump_allocator now dumps the size of the memnodes and not the last used
  free size. Also dump the total size.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1352909 13f79535-47bb-0310-9956-ffa450edef68