(Q_denotational): New variable.

(Q_denotational): New variable.
(Q_denotational_from): New variable.
(Fchar_feature): Refer `<-denotational' as same as `<-unified'.
(put_char_attribute): New function.
(Fput_char_attribute): Use `put_char_attribute'; regard
`->denotational' and `<-denotational' as same as `->unified' and
`<-unified'.
(syms_of_chartab): Add new symbols `->denotational' and
`<-denotational'.