Follow-up to r1591005: Fix the windows build.

* subversion/libsvn_fs_fs/cached_data.c
  (get_fulltext_partial): We can't do pointer arithmetics with void*.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1591018 13f79535-47bb-0310-9956-ffa450edef68