iterate

This method gives this a chance to check if some functions to be executed have finished for the calling thread.

In this case it handles the execution result and makes it ready to be processed using fetch_result.

This method also allows this to handle signals which may have been emitted by objects while in the worker thread, and call the callback function specified when connect_raw was used.

If may_block is true, then it will block untill there is one finished execution (functions returning void and signals are ignored regarding this argument).

Parameters: