loader assumes <= 128k elf file

[convolvatron]

the long term solution for this issue is to fold stage2 into stage1 so the load exactly match what is needed for the segments.

however, since the extended read call under qemu fills it what it can before returning an error, and the elf image defines the length of the 'drive', we can really just read contiguously until error. need to fix the reporting of the allocated base to stage2 and the application

[convolvatron]

fixed in hwmono branch - we actually need to do this load in protected mode in order to address
enough space, so there is a new slow ioport based disk driver that can be called from there