[$] Varlink: a protocol for IPC

One of the motivations behind projects like kdbus and bus1, both of which have fallen short ofmainline inclusion, is to have an interprocess communication (IPC)mechanism available early in the boot process. The D-Bus IPCmechanism has a daemon that cannot be started until filesystems are mountedand the like, but what if the early boot process wants to perform IPC? A new project, varlink, wasrecently announced; it aimsto provide IPC from early boot onward, though it does not really addressthe longtime D-Bus performance complaints that also served as motivationfor kdbus and bus1.