LUA_T* represents only types; tags (types + Variants) are represented
by LUA_V* constants.

Function names in the API use only lowercase letters.

Added new functions to dynamically set the C-stack limit
('lua_setCstacklimit' in the C-API, 'debug.setCstacklimit' in Lua).

This new field gets the length of 'source' in the same structure.
Unlike the other strings in that structure, 'source' can be
relatively large, and Lua already has its length readily available.

- The warning functions get an extra parameter that tells whether
message is to be continued (instead of using end-of-lines as a signal).

- The user data for the warning function is a regular value, instead
of a writable slot inside the Lua state.

Errors in finalizers (__gc metamethods) are never propagated.
Instead, they generate a warning.

The warning system is just a way for Lua to emit warnings, messages
to the programmer that do not interfere with the running program.

New functions to reset/kill a thread/coroutine, mainly (only?) to
close any pending to-be-closed variable. ('lua_resetthread' also
allows a thread to be reused...)