Merge from vendor branch TNF:

Merge from vendor branch TNF:
Initial import of lutok, version 0.1:

Lutok is a lightweight C++ API library for Lua.

Lutok provides thin C++ wrappers around the Lua C API to ease the
interaction between C++ and Lua.  These wrappers make intensive use of
RAII to prevent resource leakage, expose C++-friendly data types, report
errors by means of exceptions and ensure that the Lua stack is always
left untouched in the face of errors.  The library also provides a small
subset of miscellaneous utility functions built on top of the wrappers.

Lutok focuses on providing a clean and safe C++ interface; the drawback
is that it is not suitable for performance-critical environments.  In
order to implement error-safe C++ wrappers on top of a Lua C binary
library, Lutok adds several layers or abstraction and error checking
that go against the original spirit of the Lua C API and thus degrade
performance.