Make indexing into LinRange preserve eltype

[sostock]

Previously, indexing into a LinRange{Int} with another range would return a LinRange{Float64}. This PR fixes that.

Before:

julia> LinRange{Int}(1,5,5)
5-element LinRange{Int64}:
 1.0,2.0,3.0,4.0,5.0

julia> LinRange{Int}(1,5,5)[1:2]
2-element LinRange{Float64}:
 1.0,2.0

After:

julia> LinRange{Int}(1,5,5)
5-element LinRange{Int64}:
 1,2,3,4,5

julia> LinRange{Int}(1,5,5)[1:2]
2-element LinRange{Int64}:
 1,2

Note that this also affects the printing of LinRange{Int} because of the way print_range is implemented.