Printing of zero-step StepRangeLen does not preserve types

[mcabbott]

Here show doesn't print something which matches the original:

julia> x = -1 .+ 0 * range(1,100f0,5)
StepRangeLen(-1.0f0, 0.0f0, 5)

julia> y = StepRangeLen(-1.0f0, 0.0f0, 5)  # copying what's printed
StepRangeLen(-1.0f0, 0.0f0, 5)

julia> x === y  # not ideal!
false

julia> x === StepRangeLen{Float32}(-1.0, 0.0, 5)  # this would be better
true

julia> x === range(-1.0f0, -1.0f0, 5)  # also OK?
true

Float64:

x64 = -1 .+ 0 * range(1,100,5)
y64 = y = StepRangeLen(-1.0, 0.0, 5)  # copying what's printed
x64 === y64  # false
x64 === range(-1.0, -1.0, 5)  # true

I'm not certain that printing range cannot go wrong.

Originally marked "ugly temporary printing, to avoid 0:0:0".