Performance of SMatrix(::StaticMatrix)

[tkoolen]

using StaticArrays, BenchmarkTools
m = rand(SMatrix{3, 3})
@btime SMatrix($m)

results in 2.470 μs (33 allocations: 1.94 KiB). This particular use case is not so interesting, but this method also creates an SMatrix from other StaticMatrix types, which is occasionally useful. PR coming.