(U+591C): Add `<-denotational@usage' for BUCS+591C; add

(U+591C): Add `<-denotational@usage' for BUCS+591C; add
ideographic-structure.
(UU+591C): Unify DJT-01939.
(A-cgnU+2158D): New abstract node.
(U-0002158D): Use `->denotational' and `->subsumptive'; add
`<-denotational' for A-cgnU+2158D.
(U+591D): Apply new conventions for glyph granularity.
(A-cgnU+3689): New abstract node.
(U+3689): Add `<-denotational' for A-cgnU+3689; apply new conventions
for glyph granularity.
(HD-TK01018830): New character; use `<-denotational' for A-cgnU+3689.
(U-000215B7): Use `->denotational' and `->subsumptive'.
(U-000215B8): Use `<-Zhouwen' for U+5924.
(BUCS+591C): New abstract node; unify A2-DJT-01939.