+ -- Lua manual says: debug.traceback ([thread,] [message [, level]])
+ -- I fathom this to mean one of:
+ -- ()
+ -- (thread)
+ -- (message, level)
+ -- (thread, message, level)
+
+ if thread == nil then -- Defaults
+ thread, message, level = coroutine.running(), message, level;
+ elseif type(thread) == "string" then