[AD] Allegro AMD64 findings

[Evert Glebbeek <eglebbk@xxxxxxxxxx>]

Ok, I finally have my shiny new AMD64 setup and working smoothly. I still
need to set it up so that I can also use it easily enough for developping
32 bit programmes and libraries such as Allegro, but for now it's ok.
Anyway, I ran into a few hickups so far. Maybe these are known issues I had
just forgotten about, maybe they're new:

 - Windows in 32 bit colour depth are really screwed up, other colour
depths work as they should. This could be a driver issue, but it's
something to look into I guess.
 - The FLI player doesn't work. It seems to, but it doesn't actually
display anything.

I'll investigate both of these, hopefully later today.
Would it be a good idea to add a configure check for the AMD 64 and disable
the buildin assembler support automatically when it its detected?

Evert