[WIP/RFC] Add unit tests for buffer.c and fileio.c

My apologies, I think I'm steering this conversation off it's intended course...

Looking at @aktau's output, it's still claiming 400MB of virtual space--it's just not resident, which makes sense--and *I missed that fact before*.  It's all demand-paged, and the OS won't give it real memory until you reference it.

Sorry for the noise.