compatibility code for v1.0

I've written this snippet of code for inclusion in PackageCompiler.jl, but it feels like it should belong somewhere here.

let M = Module() # Prevent this from putting anything into the Main namespace
    # get a local reference to any module that may be directly referenced in the `precompile.jl` file
    for m in Base.loaded_modules_array()
        Core.isdefined(M, nameof(m)) || Core.eval(M, Expr(:const, Expr(:(=), nameof(m), m)))
    end
    for n in names(Main)
        if Core.isdefined(Main, n) && isconst(Main, n)
            m = getfield(Main, n)
            m isa Module && (Core.isdefined(M, nameof(m)) || Core.eval(M, Expr(:const, Expr(:(=), nameof(m), m))))
        end
    end
    Base.include(M, \"precompile.jl\")")
end # let

Start by reviewing the compatibility snippet in the issue and how it relates to PackageCompiler.jl and the precompile.jl entry point. Determine where this logic could belong in SnoopCompile.jl and whether it can be integrated without polluting Main; done means the ownership and integration approach are settled and the compatibility behavior is covered.