title: emit and slots order execution
body: <p>One thread do an <code>emit signal1();</code></p>
  
  <p>A second thread do an <code>emit signal2();</code> after that first thread has sent its signal ( there is the same mutex locked before emit call on both thread and I logged it, I can see in my log that first thread acquire lock before second thread)</p>
  
  <p>first thread and second thread or not the GUI thread.</p>
  
  <p>Is there any guarentees that signal1's slot will be call before signal2's slot ?</p>