(Fget_char_attribute): If ATTRIBUTE is a name of charset, it is

(Fget_char_attribute): If ATTRIBUTE is a name of charset, it is
regarded as a charset.
(put_char_attribute): New function in UTF-2000.
(Fput_char_attribute): If ATTRIBUTE is a charset or a name of charset,
mapping-table of the charset is modified.
(Fdefine_char): New function in UTF-2000.
(Fset_charset_mapping_table): Use `put_char_attribute' instead of
`Fput_char_attribute'.
(syms_of_mule_charset): Add new function `define-char' and new symbol
`ucs' in UTF-2000.
(vars_of_mule_charset): Update `utf-2000-version' to 0.11 (Shiki).