Set the allowNonUtf8StringLiterals option to the specified value and return a non-const reference to this tokenizer. If the allowNonUtf8StringLiterals value is false this tokenizer will check string literal tokens for invalid UTF-8, enter an error mode if it encounters a string literal token that has any content that is not UTF-8, and fail to advance to subsequent tokens until reset is called. By default, the value of the allowNonUtf8StringLiterals option is true. The behavior is undefined unless e_RELAXED == conformanceMode().