ReflectionZendExtension: add basic description (#5654)

Author: DanielEScherzer

reference/reflection/reflectionzendextension.xml

@@ -10,9 +10,10 @@
 <!-- {{{ ReflectionZendExtension intro -->
   <section xml:id="reflectionzendextension.intro">
    &reftitle.intro;
-   <para>
-
-   </para>
+   <simpara>
+    The <classname>ReflectionZendExtension</classname> class reports
+    information about a zend extension.
+   </simpara>
   </section>
 <!-- }}} -->