Add test for stencil with multiple input arrays.
Add test for stencil with multiple input arrays.

stonebig/numba,seibert/numba,IntelLabs/numba,cpcloud/numba,gmarkall/numba,stuartarchibald/numba,numba/numba,stuartarchibald/numba,seibert/numba,sklam/numba,jriehl/numba,stuartarchibald/numba,stonebig/numba,cpcloud/numba,jriehl/numba,cpcloud/numba,gmarkall/numba,numba/numba,jriehl/numba,gmarkall/numba,seibert/numba,cpcloud/numba,IntelLabs/numba,sklam/numba,stuartarchibald/numba,IntelLabs/numba,stonebig/numba,IntelLabs/numba,numba/numba,gmarkall/numba,jriehl/numba,seibert/numba,stonebig/numba,stuartarchibald/numba,sklam/numba,gmarkall/numba,IntelLabs/numba,sklam/numba,seibert/numba,stonebig/numba,numba/numba,jriehl/numba,cpcloud/numba,sklam/numba,numba/numba