Remove some unused parameters.

* subversion/libsvn_wc/props.c
  (apply_single_prop_delete,
   apply_single_mergeinfo_prop_change,
   apply_single_generic_prop_change): Remove unused parameters.
  (apply_single_prop_change, svn_wc__merge_props): Adjust callers.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1427824 13f79535-47bb-0310-9956-ffa450edef68