Add argument name suffix

Otherwise, cwise ends up generating invalid code when there's more than 9 arguments.

Was checking out ndarray-stencil and got this:

``` javascript
arr0[ptr0]=scalar0(
arr1[ptr1],
arr2[ptr2],
arr3[ptr3],
arr4[ptr4],
arr5[ptr5],
arr6[ptr6],
arr7[ptr7],
arr8[ptr8],
arr0[ptr0]0
)
```

Simple fix :)