Fixed tests.
  * "and \[\r] more", "even\[\f] more"
    Made expected output consistent with input.
  * "\x0027;\x0022; <...> \x000D;\x0009;\x000B;"
    Inserted a forgotten UTF-8 chunk for '\x0000;'
  * test_strings_long.c
    Removed explicit LINE FEED. This should be inserted by
    create_context_from_buffer().
  * Added some more crucial tests:
      o hexcoded non-BMP character
      o forgotten ; of hexcoded char
      o one more invalid hexcoded char