* Any pad can control the menu
== DETAILS
I am not sure I've quite got it so that any pad can *open* the
menu, but I do have it so any pad can control it.
- split out the input processing into a separate method
- track down and squish some hairy bugs that boiled down to
bad pointer math
- it looks like `menu_driver.c` has a mix of line endings, so I
ran it through `dos2unix` so it has consistent line endings
again.
- verified that this change did not impact actual cores
* optimize out cumulative_bits
* Incorporate PR feedback
Many thanks to @jdgleaver for providing these optimizations.
* apply one more optimization