title: Siddhi query for event prior to another within time limit
body: <p>I am trying to write a Siddhi query to detect if an event didn't happen prior to another within a time limit. The query I have to detect if 'X' didn't ever happen prior to 'Y' in the entire life of the siddhi application is:</p>
  
  <pre><code>from stream[value == 'Y']
  and not stream[value == 'X']
  </code></pre>
  
  <p>I assumed adding a time constraint would work:</p>
  
  <pre><code>from stream[value == 'Y']
  and not stream[value == 'X'] for 5 min
  </code></pre>
  
  <p>However, the 'for' statement never has any effect that I can see. This query is still triggered whether 'X' was 4 minutes ago or 6 minutes ago. I understand that a similar effect can be achieved by checking if 'Y' comes after 'X' within a time limit, but for my purposes I need to know the other way around.</p>
  
  <p>Is this possible with Siddhi? If so can someone please provide a sample query that could achieve this?</p>