(fill_char_table): Initialize `ct->unloaded'.

(fill_char_table): Initialize `ct->unloaded'.
(Fput_char_attribute): Set XCHAR_TABLE_UNLOADED(table) if
HAVE_DATABASE is defined.
(char_attribute_table_to_load): New variable of UTF-2000 with external
database support.
(Qload_char_attribute_table_map_function): Likewise.
(Fload_char_attribute_table_map_function): New function of UTF-2000
with external database support.
(Fload_char_attribute_table): New function of UTF-2000.
(Fmap_char_attribute): Call Fload_char_attribute_table if
CHAR_TABLE_UNLOADED(ct) is set when HAVE_DATABASE is defined.
(syms_of_chartab): Add new symbol and function
`load-char-attribute-table-map-function' in UTF-2000 with external
database support; add new function `load-char-attribute-table' in
UTF-2000.