[OpenBIOS] patch: machine dependent config

[Stefan Reinauer]

Hi,

ok, this time I redid the patch to make paflof sane on 64bit platforms
in a cleaner way, using abstracted defines that are dependent on certain
platform specifics. As this is platform dependent stuff which has
basically nothing to do with paflof itself, I moved it to a new file:
machdep.h. I moved the sanity check out of paflof.c into machdep.c, 
which we will probably not need to link in case we know an
architecture/compiler combination is sane.

We really need to make sure we are 64bit clean from the beginning so we 
recognize early what problems we might have to face getting paflof 
portable.

Segher, is this ok to check in from your side? If so, please do!

Stefan