amd64 register names used in the i486 tree in b17

[steve goldman]

Florian Weimer wrote:
> Someone has run s/eax/rax et al. on the i486 part of the source tree,
> which seems incorrect:

It's hard when you can't see the putback messages. The i486/amd64
directories are going to be merged into a single x86 directory soon.
This is just one of the steps to get there. We had to choose a common
naming convention and the "r"'s won. Eventually this will get us a 64bit 
c1 and 64bit tiered compilation.

-- 
Steve