extract_format
id_fmt = extract_format(id_norm, msgid, osz);
str_fmt = extract_format(str_norm, msgstr, nsz);
plural_fmt = extract_format(plural_norm, plural, nsz);
pstr_fmt[i] = extract_format(pstr_norm[i],
olen = extract_format(torg, ofmt, osz, 0);
nlen = extract_format(new, nfmt, nsz, strict);