title: ST_Within incorrectly returns true when a point is outside a polygon
body: <p>This query to determine whether a point is within a polygon...</p>
  
  <pre><code>SELECT ST_Within
  (
      ST_GeogPoint(69.6, 21.1),
      ST_GeogFromText('POLYGON((67.8 23.4, 69 17, 72.8 16.9, 67.8 23.4))')
  )
  </code></pre>
  
  <p>...returns TRUE in BigQuery.  This is an incorrect result.</p>
  
  <p>The same query...</p>
  
  <pre><code>SELECT ST_Within
  (
      ST_MakePoint(69.6, 21.1),
      'POLYGON((67.8 23.4, 69 17, 72.8 16.9, 67.8 23.4))'
  )
  </code></pre>
  
  <p>...returns FALSE in PostGIS.  This is a correct result.</p>