Day 3 part 2: ...and Uxn-ing!

Later in the night I decided to take on fixing one bug that had left me baffled in my Uxn emulator library after a week of not being able to track it down.

It left both me and neauoire puzzled in the #uxn IRC channel as to what could go wrong until d_m suggested:

<d_m> wolfdog: one annoying but simple test would be to create a file with
      something like `|100 #aa #bb #cc ___ #010e DEO #800f DEO BRK`
<d_m> and if you make it through all of those and all the outputs are identical
      i can suggest similar load/store tests

I was getting prepared to spend like 30 minutes just testing each opcode until I got to DUPk.

And then it was obvious. My code was doing the following:

DUP :=
    a := peek from stack
    push a to stack

See the problem? peek is bypassing the keep mode machinery! It should've been:

DUP :=
    a := pop from stack
    push a to stack
    push a to stack

After that simple fix, everything started working just fine. That was a fun nighttime activity, I guess.