Use better constructs where possible
- <<< instead of echo|
- Parameter expansions instead of `cut`
- Etc.
Improves performance and reliability somewhat
Also, accept "d" between diff line info parts
This script allows diffing two Game Boy ROMs using `xxd` and `diff` and
attempts to augment the diff using information pulled from SYM files.
It's not part of RGBDS proper, but can be useful to debug tests (when ROMs fail
to match).
