Modify the handling of @ symbol when specifying the check range

It looks like the @ symbol does not behave as defined in http://nagiosplug.sourceforge.net/developer-guidelines.html#THRESHOLDFORMAT.  In the range code the @ symbol changed the range 10:20 from alerting on x < 10 or x > 20 to alerting on x <= 10 or x >= 20, when it should have change it to alerting on x >= 10 or x <= 20.

Because the spec is a bit difficult to understand, I generated this table.
<table>
  <tr>
    <th>Range</th>
    <th>Generate an alert if x</th>
  </tr>
  <tr>
    <td>10</td>
    <td>x &lt; 0 or x &gt; 10, (x does not alert if x &gt;= 0 or x &lt;= 10)</td>
  </tr>
  <tr>
    <td>@10</td>
    <td>x &gt;= 0 or x &lt;= 10, (x does not alert if x &lt; 0 or x &gt; 10)</td>
  </tr>
  <tr>
    <td>10:</td>
    <td>x &lt; 10, (x does not alert if x &gt;= 10)</td>
  </tr>
  <tr>
    <td>@10:</td>
    <td>x &gt;= 10, (x does not alert if x &lt; 10)</td>
  </tr>
  <tr>
    <td>~:10</td>
    <td>x &gt; 10, (x does not alert if x &lt;= 10)</td>
  </tr>
  <tr>
    <td>@~:10</td>
    <td>x &lt;= 10, (x does not alert if x &gt; 10)</td>
  </tr>
  <tr>
    <td>10:20</td>
    <td>x &lt; 10 or x &gt; 20, (x does not alert if x &gt;= 10 or x &lt;= 20)</td>
  </tr>
  <tr>
    <td>@10:20</td>
    <td>x &gt;= 10 and x &lt;= 20, (x does not alert if x &lt; 10 or x &gt; 20)</td>
  </tr>
</table>

So, with the above information, I changed the specs to match the above table.  Then I went and modified the range code to handle the change in the specs.