Merge r1443929 from trunk:

 * r1443929
   Introduce a subpool.
   Justifcation:
     Better server memory use.
   Votes:
     +1: philip, ivan, rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.7.x@1454237 13f79535-47bb-0310-9956-ffa450edef68