Generic int 13h driver

[Die Gestalt]

w00t the driver is finished! I had to do some obscure things for the
physical memory, but I made it work. I can mount partitions, etc. do
whatever. I'll have to do some stress tests though.

It's quite slow, but that's not horrible, around 5 MB/s. However multi
threaded performance will be horrible because of the lock on physical
memory.

That could make a nice talk at a BSD conference. ;)