Fix a bug in the ASN1OctetString.stringValue(StringBuilder) method when dealing
with strings containing non-ASCII characters.  There were two problems:

- The method did not have a return statment after appending the remainder of
  the string once it was determined to be non-ASCII.

- The method did not use the UTF-8 character set when decoding the remainder of
  the string once it was determined to be non-ASCII.