Fix multiplying dual vector with symmetric/hermitian of banded matrix

[KlausC]

It is not possible to multiply a dual vector with a Symmetric{BandedMatrix}:

julia> n = 3; rand(n)' * Symmetric(BandedMatrix(0=>ones(n), 1=>ones(n-1)))
ERROR: MethodError: *(::Adjoint{Float64,Array{Float64,1}}, ::Symmetric{Float64,BandedMatrix{Float64,Array{Float64,2},Base.OneTo{Int64}}}) is ambiguous. Candidates:
  *(x::Adjoint{T,var"#s826"} where var"#s826"<:(AbstractArray{T,1} where T) where T, A::AbstractArray{T,2} where T) in LinearAlgebra at /home/crusius/julia-1.5.1/share/julia/stdlib/v1.5/LinearAlgebra/src/matmul.jl:133
  *(A::AbstractArray{T,2} where T, B::Symmetric{var"#s622",var"#s623"} where var"#s623"<:(ArrayLayouts.LayoutArray{T,2} where T) where var"#s622") in ArrayLayouts at /home/crusius/.julia/dev/ArrayLayouts/src/ArrayLayouts.jl:149
Possible fix, define
  *(::Adjoint{T,var"#s826"} where var"#s826"<:(AbstractArray{T,1} where T) where T, ::Symmetric{var"#s622",var"#s623"} where var"#s623"<:(ArrayLayouts.LayoutArray{T,2} where T) where var"#s622")
Stacktrace:
 [1] top-level scope at REPL[15]:1

[dlfivefifty]

Pushed a fix: df62537

Note at the moment I'm handling these ambiguities as they come, though it might be better to use Test.detect_ambiguities. Unfortunately I don't have time to do that right now.