Allow to execute pcall(error(T)) when T is a table

Hi,
I would like to be able to propagate more complex structures (tables) through pcall, especially:
```
Error = {["type"] = "error_type", ["msg"] = "error_msg"}
local status, result = pcall(function() error(Error) end)
if not status then
    print(result.type, result.msg)
end
```