function storeCoordIJ(cAddress, {i, j}) {
    C.setValue(cAddress, i, 'i32');
    C.setValue(cAddress + SZ_INT, j, 'i32');
}
Store an {i, j} pair to a C CoordIJ struct.
@private
@param  {number} cAddress    Pointer to C memory
@param {CoordIJ} ij          {i,j} pair to store
@return {void}