Add section IDs to the two gmirror examples to be used as direct links.

svn path=/head/; revision=41911

en_US.ISO8859-1/books/handbook/geom/chapter.xml

@@ -305,7 +305,7 @@ Done.</screen>
 	the disk and does not conflict with &man.gmirror.8;.</para>
     </sect2>
 
-    <sect2>
+    <sect2 id="GEOM-mirror-two-new-disks">
       <title>Creating a Mirror with Two New Disks</title>
 
       <para>In this example, &os; has already been installed on a
@@ -428,7 +428,7 @@ Done.</screen>
 	single drive.</para>
     </sect2>
 
-    <sect2>
+    <sect2 id="GEOM-mirror-existing-drive">
       <title>Creating a Mirror with an Existing Drive</title>
 
       <para>In this example, &os; has already been installed on a