fix Libdl loading

[bicycle1885]

This suppresses WARNING: Base.Libdl is deprecated, run `using Libdl` instead warnings.

[bicycle1885]

For clarity, I started to see these warnings on Julia 0.7-beta2.

[stevengj]

Probably import instead of using since we call Libdl via qualified names?

[bicycle1885]

I think whichever will work as we can see from the CI results (Windows failure would be a noise as usual). If you adhere to the import style, I will update the pull request.

[stevengj]

Actually, I'm confused, what is using Libdl here?

[bicycle1885]

deps/deps.jl generated by BinaryProvider.jl contains code like this:

    if Libdl.dlopen_e(libblosc) == C_NULL
        error("$(libblosc) cannot be opened, Please re-run Pkg.build(\"Blosc\"), and restart Julia.")
    end

So, I think we need to import Libdl somewhere before including the file.

[stevengj]

It looks like this should be fixed in BinaryProvider: JuliaPackaging/BinaryProvider.jl#89

[bicycle1885]

Okay, it makes sense.