Fix an off-by-one issue when comparing property names.  If I'm not mistaken,
the old code should consider "svn:date123" equivalent to "svn:date".

Due to our namespace rules, this should not turn into a real-world problem
but it is still a bug.

* subversion/libsvn_repos/fs-wrap.c
  (svn_repos_fs_revision_prop): compare the whole string - not just a prefix


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1483557 13f79535-47bb-0310-9956-ffa450edef68