Use `->subsumptive' for some character definitions.

Use `->subsumptive' for some character definitions.
(U+6902): Use `->denotational' and `->subsumptive'.
(U+6903): Likewise.
(U+3B87): Use `->denotational'.
(JX2-2F28): Use `<-denotational' for U+3B87; unify GT-19138 and
AJ1-17826.
(U+6982): Use `<-denotational' for B-B7A7.
(B-B7A7): New abstract character.
(JX2-2F34): Unify GT-19532 and AJ1-17834.
(U+6997): Use `->denotational'.
(U+69E9): Use `->denotational' and `->subsumptive'; integrate
AJ1-16912 and GT-19860.
(U+69EA): Use `->denotational' and `->subsumptive'.
(U+3BCD): Use `->subsumptive'; integrate AJ1-17848.
(U-0002383D): Use `->denotational'.
(JX2-2F75): Unify GT-20507 and AJ1-17885.