Enable parallel processing in Windows

[choisant]

Test and in the case that it does not work, fix parallel processing when running in Windows.

[pglpm]

It works (used it myself, and also Simen has used it I think).

Possibly the only point to check is that Windows uses a different protocol to open parallel cores. Possibly one has to add the argument type="FORK" when creating the clusters in Windows. But it looks like the newer versions of doParallel choose the right type automatically. Otherwise one can add a simple if-condition like

if(.Platform$OS.type == "windows") {...}

Let's check.

[choisant]

Great! Then we can choose to either state in the description that inferno requires at least version x.x of doParallel, or we add the code to support that case.