Formatting and docstring fixes.  No functional change.

* subversion/libsvn_fs_fs/index.c
  (p2l_page_info_baton_t): Fix typo in docstring.
  (read_entry): Remove space from empty line.
  (get_p2l_page): Complete docstring.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1623377 13f79535-47bb-0310-9956-ffa450edef68