(Q_circled_of): New variable.

(Q_circled_of): New variable.
(put_char_composition): Return `<-circled' instead of `=decomposition'
for compatibility mapping to single character tagged `circle'.
(Fput_char_attribute): Convert char-specs in value of
`{<-|->}circled[^*]*' to characters and put reverse links.
(Fsave_char_attribute_table): Use `Fchar_refs_simplify_char_specs' for
`<-circled'.
(syms_of_chartab): Add new symbol `<-circled'.