title: Highcharts Tootip in wrong location for multiple x axis
body: <p>I've got a chart with two x axis side-by-side, with one series in each.  When I float over the Series 1 data, I see the tooltip, as expected.  When I float over Series 2 data, it highlights the line, but no tooltip.  However, if I move the cursor to the left at the same height as the data in Series 2 data, but above the Series 1 data, the tooltip shows the Series 2 information, and the Series 2 points are highlighted.  Here's an example:</p>
  
  <p><a href="http://jsfiddle.net/q0gphwx2/5/" rel="nofollow">http://jsfiddle.net/q0gphwx2/5/</a></p>
  
  <p>Is there a way to correct for this?  </p>
  
  <pre><code>$(function () {
  $('#container').highcharts({
      chart: {
          zoomType: 'xy'
      },
  
      plotOptions : {
          area : {
              stacking : 'normal',
          }
      },
  
      title: {
          text: 'Tooltip Hover Anomoly'
      },
      subtitle: {
          text: 'Float over Series 2 data, then stay at same height, but over series 1.  '
      },
      xAxis: [{
          width:300,
          categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
              'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
      },{
          left: 400,
          width: 300,
          offset:0,
          categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
              'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
      }
  
             ],
      yAxis: [{ // Secondary yAxis
          gridLineWidth: 0,
          title: {
              text: 'Rainfall',
              style: {
                  color: Highcharts.getOptions().colors[0]
              }
          },
          labels: {
              format: '{value} mm',
              style: {
                  color: Highcharts.getOptions().colors[0]
              }
          }
  
      }],
      tooltip: {
          shared: false
      },
      series: [{
          name: 'Series 1',
          type: 'line',
          xAxis: 0,
          stack: 0,            
          data: [10, 20, 30, 40, 50, 40, 30, 20, 10, 20, 30],
          tooltip: {
              valueSuffix: ' mm'
          }
  
      }, {
          name: 'Series 2',
          type: 'line',
          xAxis: 1,
          stack: 1,
          data: [100, 120, 100, 120, 100, 120, 100, 120, 100, 120, 100, 120],
          tooltip: {
              valueSuffix: ' mm'
          }
  
      }]
  });
  });
  </code></pre>