(unibyte_char_to_multibyte):

(unibyte_char_to_multibyte):
Vnonacii_translation_table will convert a 7-bit charcater.
(multibyte_char_to_unibyte): Handle the case that
Vnonacii_translation_table converts a multibyte charcater to a
unibyte charcter of less than 128.
(init_charset_once): Initialize nonascii_insert_offset and
Vnonacii_translation_table.