Stop propagating the merge_target_t structure into so many subroutines.  No
functional change.

* subversion/libsvn_wc/merge.c
  (get_prop, maybe_update_target_eols, do_text_merge, do_text_merge_external):
    Take just the parameters that we need.
  (detranslate_wc_file, merge_text_file, svn_wc__internal_merge):
    Update callers.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1432229 13f79535-47bb-0310-9956-ffa450edef68