Now that all driver lookups in the autoconfig code are handled by string
matches, it's time to do the same thing with attachment lookups.  This
implements that.

It is worth noting that most of the config changes I'd had to deal with
have been related to the lack of a ctor/dtor facility in our kernel.  I
will probably address that in the near future.  With ctors/dtors, a lot
of this glue can go away.

I plan on checking this in fairly soon (I need to fix up the amiga/atari/x68k
console configuration code to use the new attachment lookup mechanism).

-- 
        -- Jason R. Thorpe <thorpej@wasabisystems.com>