Add glyph-images of HNG-KHM.

Add glyph-images of HNG-KHM.
(U+63DA): Separate UU+63DA.
(UU+63DA): Add `=>ucs@iwds-1'.
(HNG-KHM0056-0): New character; add `<-denotational' for U+63DA.
(U+640D): Separate UU+640D.
(MJ012599): New character; add `<-denotational' for U+640D; unify
HD-KS139720 and MH-0210; add `<-vulgar' for UU+640D; add
HNG-KHM0053-0.
(BUCS+64CA): New abstract node.
(U+6483): Add `<-denotational' for BUCS+64CA.
(HNG-KHI0078-0): Use BUCS+64CA instead of U+6483 as the mother; add
`<-formed' for U+6483 and U+64CA.
(HNG-KHM0351-0): New character; add `<-denotational' for BUCS+64CA;
add `<-formed' for U+6483 and U+64CA.
(U+64CA): Add `<-denotational' for BUCS+64CA.