Log Message:
Update to version 5.0.

* Changes from version 4.0 to 5.0
  -------------------------------
  Language:
  + lexical scoping.
  + Lua coroutines.
  + standard libraries now packaged in tables.
  + tags replaced by metatables and tag methods replaced by metamethods,
    stored in metatables.
  + proper tail calls.
  + each function can have its own global table, which can be shared.
  + new __newindex metamethod, called when we insert a new key into a table.
  + new block comments: --[[ ... ]].
  + new generic for.
  + new weak tables.
  + new boolean type.
  + new syntax "local function".
  + (f()) returns the first value returned by f.
  + {f()} fills a table with all values returned by f.
  + \n ignored in [[\n .
  + fixed and-or priorities.
  + more general syntax for function definition (e.g. function a.x.y:f()...end).
  + more general syntax for function calls (e.g. (print or write)(9)).
  + new functions (time/date, tmpfile, unpack, require, load*, etc.).
  API:
  + chunks are loaded by using lua_load; new luaL_loadfile and luaL_loadbuffer.
  + introduced lightweight userdata, a simple "void*" without a metatable.
  + new error handling protocol: the core no longer prints error messages;
    all errors are reported to the caller on the stack.
  + new lua_atpanic for host cleanup.
  + new, signal-safe, hook scheme.
  Implementation:
  + new license: MIT.
  + new, faster, register-based virtual machine.
  + support for external multithreading and coroutines.
  + new and consistent error message format.
  + the core no longer needs "stdio.h" for anything (except for a single
    use of sprintf to convert numbers to strings).
  + lua.c now runs the environment variable LUA_INIT, if present. It can
    be "@filename", to run a file, or the chunk itself.
  + support for user extensions in lua.c.
    sample implementation given for command line editing.
  + new dynamic loading library, active by default on several platforms.
  + safe garbage-collector metamethods.
  + precompiled bytecodes checked for integrity (secure binary dostring).
  + strings are fully aligned.
  + position capture in string.find.
  + read('*l') can read lines with embedded zeros.