Follow-up on r1559912:  Docstring & formatting fixes.
No functional change.

* subversion/include/svn_fs.h
  (svn_fs_path_change2_t): Mark new stuct member as 'new in 1.9'.

* subversion/libsvn_fs_fs/low_level.c
  (write_change_entry): Fix indentation.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1560107 13f79535-47bb-0310-9956-ffa450edef68