loader: kpse emulation is still wrong, see kpathsea's manual 4.2

modutils
--------

- Renaming:
    \luatexUseModule
    \luatexRequireModule
- syntax of public TeX macros and Lua functions
- create private functions for infwarrerr?
- review logic (see what LaTeX2e does)
- General review of code and comments.
- Update user documentation.

mcb
---

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

luatexbase
----------

- create it, make it load the others (except maybe mcb for now)
- create general documentation

afterwards
----------

- Bump version number, upload.