(U-0002151D): Add `sound@ja/on'.

(U-0002151D): Add `sound@ja/on'.
(IU+2151D): Add `<-ancient' for UU+78EC.
(U+58F0): Add A2-DJT-01906 as a target of `<-denotational@usage'; add
`ideographic-structure'; add `sound@ja/on'.
(UU+58F0): Unify DJT-01906; add `<-vulgar' for IU+2151D and UU+8072.
(U+58F1): Add `<-denotational@usage' for BUCS+58F9.
(UU+58F1): Unify DJT-00942.
(U+58F9): Add `<-denotational@usage' for BUCS+58F9; use
`ideographic-structure@apparent' instead of `ideographic-structure'.
(UU+58F9): Use `ideographic-structure@apparent' instead of
`ideographic-structure'; unify DJT-01909.
(A2-DJT-01906): New abstract node.
(BUCS+58F9): New abstract node; unify A2-DJT-01909.