if fmt is table and has __tostring__ then use it

[orian]

This makes logger behaviour more in sync with standard print function.

[Tieske]

just browsing through this...

There is no __tostring__ functionality in Lua, that must be some non-standard implementation. There only is the __tostring metamethod that can be put on a metatable. And that metamethod is already supported, as the logger in the end falls back on a tostring call which will invoke the __tostring method.

So this should not be merged imo.