Fix REML documentation and help topic

* REML docs in Docs/Design/reml.html has duplicate ¢ character
entity entry.
* REML help topic was never updated for the new ' character entity.

Fixes #131

Author: delphidabbler

Docs/Design/reml.html

@@ -524,10 +524,6 @@ <h1>
         <td><code>&amp;deg;</code></td>
         <td>°</td>
       </tr>
-      <tr>
-        <td><code>&amp;cent;</code></td>
-        <td>¢</td>
-      </tr>
       <tr>
         <td><code>&amp;laquo;</code></td>
         <td>«</td>

Src/Help/HTML/reml.htm

@@ -353,6 +353,10 @@ <h3 id="entities">
           <td><code>&amp;iquest;</code></td>
           <td class="centre">&iquest;</td>
         </tr>
+        <tr>
+          <td><code>&amp;apos;</code></td>
+          <td class="centre">&apos;</td>
+        </tr>
       </tbody>
     </table>
     <p>