Fix iterpool usage when filtering self-referential mergeinfo.
Fix iterpool usage when filtering self-referential mergeinfo.

* subversion/libsvn_client/merge.c
  (filter_self_referential_mergeinfo): Actually clear the iterpool and then
   use it as much as possible in the loop; only the filtered properties
   need be allocated in the passed-in pool.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion