Export @optlevel - Update exports.jl

[PallHaraldsson]

No description provided.

[vchuravy]

Why would we export from Base something that is explicitly in Base.Experimental?

julia> Base.@optlevel
ERROR: LoadError: UndefVarError: `@optlevel` not defined
in expression starting at REPL[1]:1

julia> Base.Experimental.@optlevel
ERROR: LoadError: MethodError: no method matching var"@optlevel"(::LineNumberNode, ::Module)

[PallHaraldsson]

Before this is merged, I'm guessing, not sure this is enough, I would like to know if both of these should be exported:
Base.Experimental.@optlevel
Base.Experimental.@max_methods 1

@optlevel is already available for years, in all currently supported versions, and it seems strange that people should use Experimental, or fair it is going away if it will not.

On the other hand, I'm thinking maybe this annotation is getting less important over time, actually possibly useless already with code precompiled to native code, already? So I want that discussion also, maybe it should rather go away (be changed to a noop)?

EDIT: I would need to make Base.@optlevel available first... it's a question, should it be available as such, or as @optlevel (I very much doubt that would conflict with real-world code out there).

One other question, even if @optlevel is getting redundant, where it is meant for, for packages, I would really like if using at the calling site were possible, would that make sense? Then a brand-new concept, and might need to be Experimental, after all, (I'm not sure how easy it would be to implement).