[[[
Add a test of svn_subst_translate_string2() to the subst_translate-test test
suite.

* subversion/tests/libsvn_subr/subst_translate-test.c
  (test_svn_subst_translate_string2_null_encoding): New test that tests
    svn_subst_translate_string2() with ENCODING set to NULL.
  (test_funcs): Add test_svn_subst_translate_string2_null_encoding().
]]]