Also:
* common.h: Increase safety of some of the macros.
Parenthesizing the macro parameters ... a best practice.
* firmware: partially-tracked source of "extra bits" messages.
Add a TODO comment for further study.
* Improve reliability of `lf em 4x70 writekey`
Authenticate w/new key after it is written.
Particularly important for glass modules,
or other tags with weaker coupling.