Fix problem exposed by r1577079.

* subversion/libsvn_ra/compat.c
  (svn_ra__locations_from_log): Make a copy of constant apr_array_header_t 
   argument before sorting it.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1577144 13f79535-47bb-0310-9956-ffa450edef68