[$] Sidestepping kernel memory management with DMEMFS

One of the kernel's primary jobs is to manage the memory installed in the
system. Over the years, though, there have been various reasons for
removing a portion of the system's memory from the kernel's view. One of
the latest can be seen in a mechanism called DMEMFS,
which is being proposed as a way to get around some inefficiency in how the
kernel keeps track of RAM.