Issue #2318: Inconsistent behavior with trailing '/'

   * subversion/libsvn_subr/path.c
     (svn_path_canonicalize): Modified to replace the trailing slash
      in the filename to @ if the last segment of the file path
      contained an @.

   * subversion/tests/libsvn_subr/path-test.c
     (test_canonicalize): Added tests.

   * subversion/test/clients/cmdline/basic_tests.py
     (basic_peg_revision): Modified to check for the @ sign and the
      trailing slash combination.