Follow-up to r1101578 and r1101635: Take better advantage of iterpools and subpools.
Follow-up to r1101578 and r1101635: Take better advantage of iterpools and
subpools.

Suggested by: gstein

* subversion/libsvn_client/merge.c

  (populate_remaining_ranges): Destroy iterpool before early return.  Use
   iterpool in place of scratch_pool where possible since we already have
   it and don't know how long the caller provided scratch pool will live.

  (record_skips,
   normalize_merge_sources,
   do_file_merge,
   do_merge,
   calculate_left_hand_side): Create iterpool earlier and/or defer its
   destruction until later and use it in place of the caller provided 
   scratch pool.

  (merge_cousins_and_supplement_mergeinfo): Use a subpool in place of the
   scratch pool for allocating some short-lived block-local variables.

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