[C++] Fix an off-by-one error in the argument arity check
[C++] Fix an off-by-one error in the argument arity check

shinh/kati,pombredanne/kati,danw/kati,google/kati,colincross/kati,colincross/kati,shinh/kati,shinh/kati,shinh/kati,danw/kati,colincross/kati,google/kati,shinh/kati,google/kati,colincross/kati,danw/kati,dalinaum/kati,dalinaum/kati,danw/kati,colincross/kati,google/kati,danw/kati,dalinaum/kati,pombredanne/kati,pombredanne/kati,dalinaum/kati,dalinaum/kati,pombredanne/kati,pombredanne/kati,danw/kati,google/kati,colincross/kati,pombredanne/kati,shinh/kati