documentation_hacking.xml: doxygen.org is now doxygen.nl.

	* doc/xml/manual/documentation_hacking.xml: doxygen.org is now
	doxygen.nl.

From-SVN: r274094

libstdc++-v3/ChangeLog

+2019-08-04  Gerald Pfeifer  <gerald@pfeifer.com>
+
+	* doc/xml/manual/documentation_hacking.xml: doxygen.org is now
+	doxygen.nl.
+
 2019-08-01  Edward Smith-Rowland  <3dw4rd@verizon.net>
 
 	Implement C++20 p0202 - Add Constexpr Modifiers to Functions

libstdc++-v3/doc/xml/manual/documentation_hacking.xml

@@ -261,7 +261,7 @@
 
       <para>
 	Prerequisite tools are Bash 2.0 or later,
-	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.doxygen.org">Doxygen</link>, and
+	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.doxygen.nl">Doxygen</link>, and
 	the <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.gnu.org/software/coreutils/">GNU
 	coreutils</link>. (GNU versions of find, xargs, and possibly
 	sed and grep are used, just because the GNU versions make