documentation_hacking.xml: Tweak link to doxygen.org.

	* doc/xml/manual/documentation_hacking.xml: Tweak link to
	doxygen.org.

From-SVN: r245808

libstdc++-v3/ChangeLog

+2017-03-01  Gerald Pfeifer  <gerald@pfeifer.com>
+
+	* doc/xml/manual/documentation_hacking.xml: Tweak link to
+	doxygen.org.
+
 2017-02-23  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/experimental/iterator: Include <iterator>.

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.org">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