Executing jldoctest blocks out of process

[amitmurthy]

It will be nice to have an option to execute jldoctest blocks in an external, spawned process. This would be an alternate option to wrapping the code block in a module before execution. Will help in addressing issues like https://github.com/JuliaLang/Distributed.jl/issues/19 . stdout of the spawned process can be used to check for correctness.

[mortenpi]

Definitely something we could consider. Should be a non-default option of a doctest I think. It will make the doctest execution much slower. Is there some API that would allow us to spawn a child Julia REPL session or something? Or should it be done with run?

Not very high priority though, so implementation is up for grabs.