__ntapi_ipc_create_pipe(): refine, change polling strategy.
    
    The canonical way of polling an i/o handle by requesting a zero-byte
    read/write operation and then waiting on the event (or apc routine) that
    was specified for that i/o operation fails to work on the writing end of
    a byte-stream pipe. Specifically, the request completes immediately,
    therefore not allowing us to employ it for a controlled poll operation.
    
    Following this patch, the writing end of the pipe is opened with the
    NT_FILE_SYNCHRONOUS_IO_ALERT flag set. With this flag set, zero-byte
    writes block, which makes them perfectly suitable for a polling operation,
    but less so for non-blocking i/o. With some effort, however, the latter
    can be achieved and be both robust and reliable.