Don't fall back to OSS when Drivers=""

[Mike Hearn]

> Not sure I see the point, could you please elaborate on what you are
> trying to achieve here?

Setting Drivers="" in the config file is supposed to prevent sound from 
being used at all - there are actually howtos and such on the net that 
say this and it's sometimes given as tech support advice, so I assumed 
it worked. But, it doesn't seem to - Drivers="" always causes 
wineoss.drv to be loaded instead. So this patch lets you to make the app 
think there are no sound cards in the machine.