RFC: client side implementation of async I/O

[Michael McCormack]

Hi all,

This patch moves responsibility for asynchronous I/O to the client process. 
i'm posting it to wine-devel because i want to know what other developers here
think about the technique i've used to make this work... i've relaxed some of
the assumptions wineserver makes about client processes.

i think this implementation is more efficient, as it makes fewer server calls
and duplicates fewer file descriptors, while maintaining correctness.

Mike