http://kcachegrind.sourceforge.net/cgi-bin/show.cgi/KcacheGrindIndex
page indicates to rather go to
https://kcachegrind.github.io/html/Home.html
so update the doc accordingly.
<!ENTITY vg-repo-url "http://www.valgrind.org/downloads/repository.html">
<!ENTITY vg-pubs-url "http://www.valgrind.org/docs/pubs.html">
<!ENTITY vg-docs-url "http://www.valgrind.org/docs/manual/index.html">
-<!ENTITY cl-gui-url "http://kcachegrind.sourceforge.net/cgi-bin/show.cgi/KcacheGrindIndex">
+<!ENTITY cl-gui-url "https://kcachegrind.github.io/html/Home.html">
<!-- Some references are used between core manual manual and manpages. -->
<!-- Define them here so the can easily be used in both places. -->