Implement a bug to have an easy test to check I'm running my verilog

I've decided to call this bug leetoverflow.  Because of course,
right?  It is implemented by inserting a bug in the ALU's adder which
changes the results anytime an add which executes 31337 + 31337 goes
through.  Instead of returning values as normal, the ALU returns 42.
This allows me to easily check and verify that I'm running the verilog I
expect I'm running.  (In the future, I'll likely change 42 to a version
number different for each interation of the codebase so I can always
have an easy way to verify my FPGA is using the verilog I think it's
using.)

It can be run as easily as executing an add instruction, but a quick
way to check in BASH is just to type: "echo $((31337+33137))"