ref-manual: Added qemu class.

(From yocto-docs rev: 85732913c2abb9b38857cec7abe12407e1be42ce)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-classes.xml

@@ -1585,6 +1585,17 @@
     </para>
 </section>
 
+<section id='ref-classes-qemu'>
+    <title><filename>qemu.bbclass</filename></title>
+
+    <para>
+        The <filename>qemu</filename> class provides functionality for recipes
+        that either need QEMU or test for the existence of QEMU.
+        Typically, this class is used to run programs for a target system on
+        the build host using QEMU's application emulation mode.
+    </para>
+</section>
+
 <section id='ref-classes-distutils'>
     <title>Python Extensions - <filename>distutils.bbclass</filename></title>