fixup /etc/fstab and anything else that might have hardwired DOS partition
information.  This is the piece of the puzzle needed for loading an image
into a partition other than the one in which it was created.  I never
installed it since there was no demand and it is one more piece on the disk
loading path that could break.

Just checking this in for the day when we might want it.  Note that it is
still not installed (i.e., I didn't change the Makefile to install it).