[$] IPC medley: message-queue peeking, io_uring, and bus1

The kernel provides a number of ways for processes to communicate with eachother, but they never quite seem to fit the bill for many users. There arecurrently a few proposals for interprocess communication (IPC) enhancementscirculating on the mailing lists. The most straightforward one adds a newsystem call for POSIX message queues that enables the addition of newfeatures. For those wanting an entirely new way to do interprocesscommunication, there is a proposal to add a new subsystem for that purposeto io_uring. Finally, the bus1 proposal has made a return after ten years.