Web out-of-order buffer size tester

This produces ASCII graphs showing the approximate sizes of various CPU
out-of-order execution resources. This is pretty inaccurate, but it's a
fun proof-of-concept. I apologise for the ASCII output.

This "tool" is mostly for entertainment purposes, at least for now.
Please don't trust it. I thought I could make it work, and I thought
it'd be insane, so I tried and it mostly works. More info on Twitter.

Works better on Safari/Chrome. This tool was originally called the
ROB size tester. As Travis pointed out, it actually measures the
PRRT (or the equivalent on Apple CPUs, which I've been calling the
"Rename Retire Queue"). This is the maximum number of in-flight
destination registers, which isn't a bad proxy for ROB size, but
operations such as stores and branches don't use entries, so it's
likely to underestimate how many instructions can be in-flight.

See also my web load/store buffer size tester.