message: Add bilingual_str::clear()
diff: @@ -28,6 +28,12 @@ struct bilingual_str {
  {
  return original.empty();
  }
  +
  + void clear()
  + {
  + original.clear();
  + translated.clear();
  + }
  };
  inline bilingual_str operator+(bilingual_str lhs, const bilingual_str& rhs)
  