[计] double-punch and blank-column detection

shuāng kǒng hé wú kǒng jiǎn cè ㄕㄨㄤ ㄎㄨㄥˇ ㄏㄜˊ ㄨˊ ㄎㄨㄥˇ ㄐㄧㄢˇ ㄘㄜˋ