"Emulate async read" parameter

[sundance2]

Thanks @SWAT ! I think this is much clearer now !

So, when instructed to load N sectors,
your loader layer intentionally cuts the request into smaller batches of size [1-16]
in order to give back control from time to time to the application,
so that it can do something useful before blocking again for next batch read.

And the option "none" essentially means "no limit" : if the application requests N sectors, it will block until it receives N sectors.

I suspect that what retrodream calls "TRUE" is essentially the same as Dreamshell "none", since it's just an overlay.

I believe what I got wrong in my mental model is that I associated "none" to `0`, because in the UI it seems positioned "before" the `1`,
while it should rather be associated with "infinity", and therefore could be considered "beyond" the `16`.