from the version used by NetBSD/alpha, with several changes by me.
Support for asking for root device and root file system type on any
kernel, obsoleting "options GENERIC".
- Make my mountroothook implementation used by the sparc and x68k
ports machine-independent, and use it here. Mountroothooks allow
devices to execute special functions before being mounted as the
root device (such as ejecting the floppy and prompting for a new
floppy disk).
- Make swapconf() machine-independent. It was identical on all ports.