Add more negative tests for decoding.
Add more negative tests for decoding.

dajohi/go-xdr,davecgh/go-xdr,rasky/go-xdr,postfix/go-xdr,rasky/go-xdr,nullstyle/go-xdr,nullstyle/go-xdr,dajohi/go-xdr,davecgh/go-xdr,postfix/go-xdr