pub fn qdtext<I, E>(input: I) -> IResult<I, char, E>where I: InputIter + Slice<RangeFrom<usize>> + Copy, <I as InputIter>::Item: AsChar, E: ParseError<I>,
QDTEXT = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text