The release engineer keeps using the wrong /boot/cdboot when creating the
ISO images. So we'll add the 4.0-RELEASE cdboot to the tree until someone
bothers to fix the source so a working `cdboot' is built.
- Make as much of the makefile for each of the three flavours
(disk, CDROM, net) common.
- Special-case the libalpha startup module on its use in boot1, not
the other way around.
- Build the loader out of a "loader" directory
Reviewed by: mjacob, dfr
* Make it possible to type a filename to boot1 so that it is possible to
recover from fatally broken versions of /boot/loader.
* Make a start at a CD boot program (not yet functional).
