Punycode decoding fails if encoded string has not hyphen

When validating host name like "xn--eckwd4c7cu47r2wf.jp", punycode decoder fails.

In typically case of Japanese(Maybe also Chinese and Korean) domain name, it hasn't ASCII characters. Then, encoded string has not hyphen after "xn--". In this case, current code reports decode error.

And, ZF1 also has this problem.