Added more unicode sub/superscripts to Latex tab completions
simplify type unions after instantiation

ref #7017

before it was possible for Union(Vector{T},Vector{Float64}) to end up as
Union(Vector{Float64},Vector{Float64}) after substituting T.
improve docs for isready(). closes #7006
Merge branch 'master' of github.com:JuliaLang/julia
Merge pull request #7018 from lstagner/sub_super

Added more unicode sub/superscripts to Latex tab completions
fix #6980, method sorting bug
Pairwise BLAS-based sumabs and sumabs2

Also speed up sum/sumabs/sumabs2 for very small vectors
Merge branch 'sjk/pairwise-sumabs2'