#34234 normalize(a) for multidimensional arrays

[ssikdar1]

PR to try and resolve issue JuliaLang/LinearAlgebra.jl#688

• Change the type signatures and documentation from AbstractVector to AbstractArray
• Change this line from v[1] to first(v). (This is a bug anyway, since v[1] is wrong for non 1-based arrays.)
• Change the documentation to refer to "array" rather than "vector" and use a rather than v. (changed docstrings)
• Add a few tests. (not sure if i need more?)
• Add a NEWS item.

Testing:
added unit test to stdlib/LinearAlgebra/test/generic.jl
ran ./julia stdlib/LinearAlgebra/test/generic.jl with no errors.

...
Test Summary:                         | Pass  Total
normalize for multidimensional arrays |    2      2
...

Testing in the shell:

julia> using LinearAlgebra;

julia> arr = [ [1.0 0.0]; [0.0 1.0] ]
2×2 Array{Float64,2}:
 1.0  0.0
 0.0  1.0

julia> @show arr
arr = [1.0 0.0; 0.0 1.0]
2×2 Array{Float64,2}:
 1.0  0.0
 0.0  1.0

julia> @show normalize(arr)
normalize(arr) = [0.7071067811865475 0.0; 0.0 0.7071067811865475]
2×2 Array{Float64,2}:
 0.707107  0.0
 0.0       0.707107

julia> @show normalize!(copy(arr))
normalize!(copy(arr)) = [0.7071067811865475 0.0; 0.0 0.7071067811865475]
2×2 Array{Float64,2}:
 0.707107  0.0
 0.0       0.707107

julia> @show normalize(arr) == normalize!(copy(arr))
normalize(arr) == normalize!(copy(arr)) = true
true

julia> arr = [[1.0 0.0 0.0]; [0.0 1.0 0.0]]
2×3 Array{Float64,2}:
 1.0  0.0  0.0
 0.0  1.0  0.0

julia> @show normalize(arr) == normalize!(copy(arr))
normalize(arr) == normalize!(copy(arr)) = true
true

julia> a = [1,0,0]
3-element Array{Int64,1}:
 1
 0
 0

julia> @show normalize(a) == normalize!(copy(a))
normalize(a) == normalize!(copy(a)) = true
true

[oscardssmith]

Should this be backported? It seems simple and is partially a bug fix

[StefanKarpinski]

No, this is definitely a feature. The bugfix part could be backported.

[ssikdar1]

The CI failures seem to be complaining about the Makefile and seem to be unrelated?

make: *** No rule to make target 'win-extras'.  Stop.

[stevengj]

LGTM. Thanks for tackling this, @ssikdar1!

[jw3126]

LGTM, thanks very much @ssikdar1 for doing this!