Change terms unify/unification to

Change terms unify/unification to
translate/translation respectively throughtout the file.
(encode_coding_iso2022): Fix bug in encoding a text ending by a
composite character.
(check_composing_code): If we are decoding the last block of data,
return 0 even if the source doesn't end by an escape sequence
which terminates the current composing sequence.
(decode_coding_iso2022): Decode correctly even if the source
doesn't end by an escape sequence which terminates the current
composing sequence.