but if not then try to boot "netbsd", "netbsd.bak", "netbsd.old", and
"onetbsd" (in that order) until one is found or until the list of names
is exhausted.
boot block, since it will be shared with the network boot block.
(2) Kill a.out support, since it never worked was never used, and will
never be.
(3) Add support for booting of ELF kernels, from Matt Thomas. (Currently
untested, but it compiles.)