Boot program changed

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

Hi all,

I have made some changes to the boot program to allow large kernels to 
be loaded.
This should solve the problems with the 8.0 boot.

The changes are quite invasive and I haven't tested all drivers yet, but 
after that I will request pullup to NetBSD 8.

-- Ragge