Update idn-to-ascii.xml: Adding info about conversion to lowercase (#4505)

This would close https://bugs.php.net/bug.php?id=80922

Author: ThomasLandauer

reference/intl/idn/idn-to-ascii.xml

@@ -16,7 +16,7 @@
    <methodparam choice="opt"><type>array</type><parameter role="reference">idna_info</parameter><initializer>&null;</initializer></methodparam>
   </methodsynopsis>
   <para>
-   This function converts a Unicode domain name to an IDNA ASCII-compatible format.  
+   This function converts a Unicode domain name to an IDNA ASCII-compatible format in lowercase.
   </para> 
   </refsect1>
 
@@ -129,6 +129,24 @@ echo idn_to_ascii('täst.de');
   <screen>
 <![CDATA[
 xn--tst-qla.de
+]]>
+  </screen>
+  <example>
+   <title>All-ASCII domain names are just converted to lowercase</title>
+   <programlisting role="php">
+<![CDATA[
+<?php
+
+var_dump(idn_to_ascii('Example.com'));
+
+?>
+]]>
+   </programlisting>
+  </example>
+  &example.outputs;
+  <screen>
+<![CDATA[
+string(11) "example.com"
 ]]>
   </screen>
  </refsect1>