Windows direct cdrom reading async support

[rakslice]

When I quickly hooked up the cdrom reading in windows because I realized that was possible that you could actually just use the drive letter handle to read the contents of a regular data disc without a special driver, I just made the implementation as simple as possible.

However it's totally synchronous; the emulator stops while I/O ops are in progress and for physical CD seeking that's a nontrivial amount of time.

When I encountered Lauri Pesonen's port code I was reminded that it did the same thing, but it actually implements async support. (I don't know how well, but I can see it at least uses the function parameters for it.)

Look into this.

While I'm at it, what is the situation in linux?

[rakslice]

Maybe look at what it does for hardfile I/O for reference