modutils
--------

- syntax of public TeX macros and Lua functions
- create private functions for infwarrerr?

- review logic: should this module be mandatory?
  if not, what should happen with mixed require(), require_module(),
declaration and no declaration?

mcb
---

- Incorporate remaining bits from luatextra?
- Enhance test file?
- General review of code and comments.
- Update user documentation.