Update some comments to match changes made years ago in r849566.
Update some comments to match changes made years ago in r849566.

* subversion/libsvn_fs_fs/tree.c
  (get_dag): Fix white space.
  (get_root): Update the parameter names.
  (merge_changes): Update the parameter names, restore documentation of the
    'conflict' parameter, and update a comment to reflect a behaviour change.

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