luautf8 needs utf8.format (to replace string.format)

[cloudranger]

Your README says "Some routines in string module needn't support Unicode: string.format"
However, this code is proof that string.format does need unicode support:

print(string.format("%-35s", "abcdefghijklmnopqrstuvwxyz"))
print(string.format("%-35s", "àb¢défghijklmnöpqrstüvwxyz"))

string.format does not count utf8 characters, it counts the number of bytes, so when you used a fixed size in the formatting string and accented characters are used, string.format gets it wrong.