Fix lots of broken links in the docs, found by Sphinx' external link checker.
diff --git a/Doc/howto/advocacy.rst b/Doc/howto/advocacy.rst
index 8b5b11c..d71e1ec 100644
--- a/Doc/howto/advocacy.rst
+++ b/Doc/howto/advocacy.rst
@@ -346,7 +346,7 @@
wasn't written commercially. This site presents arguments that show how open
source software can have considerable advantages over closed-source software.
-http://sunsite.unc.edu/LDP/HOWTO/mini/Advocacy.html
+http://www.faqs.org/docs/Linux-mini/Advocacy.html
The Linux Advocacy mini-HOWTO was the inspiration for this document, and is also
well worth reading for general suggestions on winning acceptance for a new
technology, such as Linux or Python. In general, you won't make much progress