Allow NtFileFlushBuffers to block

[Eric Pouech]

> ChangeLog:
> * allow NtFileFlushBuffers to block, as flushing a named pipe requires this

what I don't like in your patch is that you create an event in all 
cases, where according to the doc, FlushFileBuffers should only block 
for named pipes.
maybe, it would be better to return the event handle from the flush 
server call and wait in kernel if this event is not NULL

A+

-- 
Eric Pouech