Adjoint for vectors may use trailing axes of the parent

[jishnub]

Close JuliaLang/LinearAlgebra.jl#1042, or at least the part that may be addressed here. After this, the first axis for an Adjoint(parent::AbstractVector) will be the second axis of the parent. This will change the type of the axis where the parent array type specializes axes(A, d). In the short term, this would improve type-stability in cases such as

julia> A = OffsetArray([1,2], 2);

julia> @code_typed axes(A')[1]
CodeInfo(
1 ─ %1 = $(Expr(:boundscheck))::Bool
│   %2 = Base.getfield(t, i, %1)::OffsetArrays.IdOffsetRange{Int64, Base.OneTo{Int64}}
└──      return %2
) => OffsetArrays.IdOffsetRange{Int64, Base.OneTo{Int64}}

where the result is now concretely inferred instead of being a small Union.
In principle, with JuliaArrays/StaticArrays.jl#916, this would make the axes of the adjoint of a StaticVector statically sized.

[dkarrasch]

Looks reasonable to me.