Added PCRE n (NO_AUTO_CAPTURE) modifier description. (#2598)

Author: mumumu

reference/pcre/pattern.modifiers.xml

@@ -174,6 +174,18 @@
        </simpara>
       </listitem>
      </varlistentry>
+     <varlistentry>
+      <term><emphasis>n</emphasis> (<literal>PCRE_NO_AUTO_CAPTURE</literal>)</term>
+      <listitem>
+       <simpara>
+        This modifier makes simple <code>(xyz)</code> groups non-capturing.
+        Only named groups like <code>(?&lt;name&gt;xyz)</code> are capturing.
+        This only affects which groups are capturing, it is still possible to
+        use numbered subpattern references, and the matches array will still
+        contain numbered results.
+       </simpara>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </blockquote>
   </para>