Add glyph-images of HNG-KHI.

Add glyph-images of HNG-KHI.
(U+6821): Apply new conventions for glyph granularity.
(U+68C3): Likewise; unify S-3656; add `<-vulgar' for U+68A8.
(U+697C): Apply new conventions for glyph granularity.
(U+697D): Likewise.
(U+3BB5): Likewise.
(U-000235F3): Unify S-3817; add `<-vulgar' for U+6A39.
(U+6A80): Apply new conventions for glyph granularity for components
of ideographic-structure.
(U+6A8F): Apply new conventions for glyph granularity.
(U-00023780): New character.
(U+3BF8): Unify M-15728.
(U-00023786): Unify M-15771.
(U-00023787): Unify M-15772.
(U-00023788): New character.
(U-0002377B): Unify M-15774.
(U-0002377E): Integrate M-15780.
(U-0002377C): Unify M-15782.