is_valid_optimized_type() rejects the markers BJData excludes, so the reader no longer needs its own list; the test now checks is_valid_optimized_type() of a BJData reader against the writer's list. The BSON size comment now says that open_bson_document() rejects a size below 5. Signed-off-by: Niels Lohmann <mail@nlohmann.me>