Changed the method to synchronize the analyzer threads: We now use QSet to maintain...

Changed the method to synchronize the analyzer threads: We now use QSet to maintain a list of the thread id's of all threads that are still running - instead of only recording the highest thread id that has finished. This way a thread can now actually check if there still is any running thread with a lower thread id. Before thread n could only check if thread n-1 has finished yet or not. As a result we can relax the waiting now. Only threads that want to emit a file will wait for the "previous" threads to finish.