Ok, here's an update. I still have no idea how to get qemu to complie, and I
would love to know the actual ./configure options you people use to compile it
succesfully, but here's the good news:
In ArchBang I got a version of Qemu new enough to not have the ISOLINUX bug. So that did
get fixed. And it is obtainable without compiling from source. I just did "sudo
pacman -S qemu".
Also, this version no longer has the "-M ?" and "-cpu ?" bug.
And it does default to 64-bit on a 64-bit machine, though to QEMU's virtual
CPU, not to the common kvm processor. I was just worried there for a little bit
that it defaults to 32-bit on a 64-bit machine.
So it's looking good. It would just be nice to know how to compile it.