`perf_laplace_sparse_matvec` doesn't seem to do any matvecs

[KristofferC]

BaseBenchmarks.jl/src/problem/Laplacian.jl

Lines 41 to 51 in 9306a27

	function laplace_sparse_matvec(n1, n2, n3)
	I_n1 = sparse(1.0I, n1, n1)
	I_n2 = sparse(1.0I, n2, n2)
	I_n3 = sparse(1.0I, n3, n3)
	D1 = kron(I_n3, kron(I_n2, ddx_spdiags(n1)))
	D2 = kron(I_n3, kron(ddx_spdiags(n2), I_n1))
	D3 = kron(ddx_spdiags(n3), kron(I_n2, I_n1))
	D = [D1 D2 D3] # divergence from faces to cell-centers
	return D*D'
	end

It is just benchmarking the setup of the sparse matrix (effectively testing sparse matmat)