Update XML Schema for new entries

Define the element cputune's child elements 'period' and 'quota':
<cputune>
  <period>100000</period>
  <quota>50000</quota>
</cputune>

docs/schemas/domain.rng

@@ -388,6 +388,16 @@
               <ref name="cpushares"/>
             </element>
           </optional>
+          <optional>
+            <element name="period">
+              <ref name="cpuperiod"/>
+            </element>
+          </optional>
+          <optional>
+            <element name="quota">
+              <ref name="cpuquota"/>
+            </element>
+          </optional>
           <zeroOrMore>
             <element name="vcpupin">
               <attribute name="vcpu">
@@ -2401,7 +2411,21 @@
     <data type="unsignedInt">
       <param name="pattern">[0-9]+</param>
     </data>
-   </define>
+  </define>
+  <define name="cpuperiod">
+    <data type="unsignedLong">
+      <param name="pattern">[0-9]+</param>
+      <param name="minInclusive">1000</param>
+      <param name="maxInclusive">1000000</param>
+    </data>
+  </define>
+  <define name="cpuquota">
+    <data type="long">
+      <param name="pattern">-?[0-9]+</param>
+      <param name="maxInclusive">18446744073709551</param>
+      <param name='minInclusive'>-1</param>
+    </data>
+  </define>
   <define name="PortNumber">
     <data type="short">
       <param name="minInclusive">-1</param>