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Description
After I have registered a callback to a luv handle, when the callback need to be called, we use luv_call_callback to call it.
It's is OK when there is no exception when calling the callback function. But when error occured, it just print the stack traceback and call exit to end the process.
I think it is better to provide an alternative way just like "uncaughtException" in nodejs to allow user to do more control.
And I think luv_call_callback should to be exported just like "MakeCallback" in NAN, so it can provide a consistent error handling machanism when I write a extension for luv.