Add doc strings and other comments.
Add doc strings and other comments.

* subversion/libsvn_client/repos_diff.c
  (close_directory, change_file_prop, change_dir_prop, absent_directory,
   absent_file): Add a doc string and other comments.

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