(A-cgnU+5EB8): New abstract node.

(A-cgnU+5EB8): New abstract node.
(U+5EB8): Add `<-denotational' for A-cgnU+5EB8; add
`<-denotational@usage' for BUCS+5EB8; use
`ideographic-structure@apparent' instead of `ideographic-structure';
add `sound@ja/on/{kan|go}'; apply new conventions for glyph
granularity.
(HNG-KAR0815-0): Use A-cgnU+5EB8 instead of A-UU+5EB8 as its mother;
use `ideographic-structure@apparent' instead of
`ideographic-structure'.
(A-MJ059558): Likewise.
(BUCS+5EB8): New abstract node; unify A2-DJT-02963.