docs: Fix documentation for cputune parameters

This re-adds the example section originally written by Osier Yang,
and indicates the version in which the cputune parameters became
available in libvirt.
Signed-off-by: NIgor Serebryany <igor47@moomers.org>

docs/formatdomain.html.in

@@ -288,6 +288,13 @@
     <min_guarantee>65536</min_guarantee>
   </memtune>
   <vcpu cpuset="1-4,^3,6" current="1">2</vcpu>
+  <cputune>
+    <vcpupin vcpu="0" cpuset="1-4,^2">
+    <vcpupin vcpu="1" cpuset="0,1">
+    <vcpupin vcpu="2" cpuset="2,3">
+    <vcpupin vcpu="3" cpuset="0,4">
+    <cpushares>2048</cpushares>
+  </cputune>
   ...</pre>
 
     <dl>
@@ -351,21 +358,30 @@
         virtual CPUs should be enabled.
       </dd>
       <dt><code>cputune</code></dt>
-      <dd> The optional <code>cputune</code> element provides details
-        regarding the cpu tunable parameters for the domain.</dd>
+      <dd>
+         The optional <code>cputune</code> element provides details
+         regarding the cpu tunable parameters for the domain.
+         <span class="since">Since 0.9.0</span>
+      </dd>
       <dt><code>vcpupin</code></dt>
-      <dd> The optional <code>vcpupin</code> element specifies which of host
+      <dd>
+        The optional <code>vcpupin</code> element specifies which of host
         physical CPUS the domain VCPU will be pinned to. If this is ommited,
         each VCPU pinned to all the physical CPUS by default. It contains two
         required attributes, the attribute <code>vcpu</code> specifies vcpu id,
         and the attribute <code>cpuset</code> is same as attribute <code>cpuset</code>
-        of element <code>vcpu</code>. NB, Only qemu driver supports</dd>
+        of element <code>vcpu</code>. (NB: Only qemu driver support)
+        <span class="since">Since 0.9.0</span>
+       </dd>
       <dt><code>shares</code></dt>
-      <dd> The optional <code>shares</code> element specifies the proportional
+      <dd>
+        The optional <code>shares</code> element specifies the proportional
         weighted share for the domain. If this is ommited, it defaults to
         the OS provided defaults. NB, There is no unit for the value, it's a relative
         measure based on the setting of other VM, e.g. A VM configured with value
-        2048 will get twice as much CPU time as a VM configured with value 1024.</dd>
+        2048 will get twice as much CPU time as a VM configured with value 1024.
+        <span class="since">Since 0.9.0</span>
+      </dd>
     </dl>
 
     <h3><a name="elementsCPU">CPU model and topology</a></h3>