Considering how much trouble a merge phase would be (commit 4978), it seems
simpler to just add the extra syntax for controlling the entry point of
the generated ELF binary.
But I wouldn't have noticed this if I hadn't taken the time to write out
the commit messages of 4976 and 4978.
Even if we happened to already have linked list primitives built, this
may still be a good idea considering that I'm saving quite a lot of code
in duplicated entrypoints.
Clean up a few things:
a) Call scan-next-byte in hex.subx with the right number of args. Turns
out tests continue to work fine if they never use the other args.
b) Tear down a test for 'stop' in the right order. Not important since we
have no EBP to restore. But can still be misleading.
c) Have 'check-ints-equal' return nothing. Handy for it to not mess up
EAX. I never use the result anyway, and the name also is imperative suggesting
callers won't expect a return value.