Overly restrictive type constraints in LinearAlgebra

[YingboMa]

Many functions in LinearAlgebra have the ::StridedVecOrMat constraint. In many cases, it seems unnecessary. Just to list a few:

https://github.com/JuliaLang/julia/blob/8a5b3233a1fad479ed417345fc2b9de0a5d23c1d/stdlib/LinearAlgebra/src/lu.jl#L394-L397
https://github.com/JuliaLang/julia/blob/8a5b3233a1fad479ed417345fc2b9de0a5d23c1d/stdlib/LinearAlgebra/src/lu.jl#L339-L389

This causes problems like

julia> using LinearAlgebra
julia> A = rand(3, 3); x = rand(3)';
julia> ldiv!(lu(A), vec(x))
ERROR: MethodError: no method matching ldiv!(::LU{Float64,Array{Float64,2}}, ::Base.ReshapedArray{Float64,1,Adjoint{Float64,Array{Float64,1}},Tuple{}})