Add glyph-images of HNG-KHM.

Add glyph-images of HNG-KHM.
(U+5721-var-002): Add `<-formed' for U+571F; add HNG-KHM0263-0.
(U+5728): Separate UU+5728.
(g2-UU+5728): Don't subsume HNG-KHI0319-0; add HNG-KHM0258-0.
(U+5728-itaiji-002): New character; add `<-denotational' for U+5728;
move HNG-KHI0319-0 from g2-UU+5728.
(HNG-KHI0031-0): Moved to Ideograph-R046-Mountain.el.
(U+5872-itaiji-001): New character to integrate HNG-KHI0321-0 and
HNG-KHM0259-0; add `<-denotational' for U+5872; add `<-formed' for
U+5834.
(HNG-KHI0321-0): Use `<-subsumptive' for U+5872-itaiji-001 instead of
`<-denotational' for U+5872.
(HNG-KHM0262-1): New character; add `<-denotational' for U+5875.
(U+58CA): Separate UU+58CA.
(UU+58CA): Add `=>ucs@iwds-1'.
(U+58CA-itaiji-002): New character; add `<-denotational' for U+58CA;
add HNG-KHM0019-0.