[math-fun] HAKMEM Munching Squares bug report!

I'm still getting bug reports for code that runs on hardware that no longer exists! "I believe HAKMEM Item 146: Munching Squares has a bug. I tried the code on a PDP-10 and 340 display emulator, but it wouldn't work. I compared against the PDP-1 version and found a difference. I think the XOR 1,2 instruction should be XOR 2,1."