Add glyph-images of HNG-KHM.

Add glyph-images of HNG-KHM.
(U+7537): Separate UU+7537.
(GT-K01666): New character; add `<-denotational' for U+7537.
(U+7537-itaiji-003): New character to subsume HNG-KHI0491-0 and
HNG-KHM0093-0; add `<-denotational' for BUCS+7537; add `<-formed' for
U+7537.
(BUCS+7562): New abstract node.
(U+7562): Add `<-denotational' for BUCS+7562.
(A-BC-87C5): New abstract character; add `<-denotational' for
BUCS+7562; unify A-MJ058090.
(HNG-KHM0094-0): New character; add `<-denotational' for A-MJ058090;
add `<-formed' for U+7562.
(MJ058090): New character; add `<-denotational' for A-MJ058090; unify
BC-87C5 and KOSEKI-244450; add `<-formed' for U+7562.
(UU+7570): Apply new conventions for glyph granularity.
(HNG-KHM0441-0): New character; add `<-denotational' for U+7570.