1.1: Initial bootst (from Dale Rahn)
1.2: Update based on sun3 tapeboot (by Chuck Cranor)
1.3: Support verbose/quiet boot.
1.4: loadfile() update: ELF symbols no longer need backward seeks.
1.5: loadfile() update to avoid backwards seeks for ELF Program Headers.
1.6: hackprom_diskrd() needs loads up to 3MB from tape for current kernels.
1.7: switched to using MI libsa and libkern