tuning fontconfig - mention WOFF fonts.

To stop people thinking that every website's choice of font can be
easily overridden (firefox can do that, not sure about other
browsers).

This is about halfway through the commits from my initial private
branch.

x/installing/tuning-fontconfig.xml

@@ -519,10 +519,13 @@ EOF</userinput></screen>
   <title>Preferring certain fonts</title>
 
     <para>
-      There are many reasons why people may wish to have pages which specify a
-      particular font use a different font, or prefer specific fonts in
-      Monospace or Sans or Serif. As you will expect, there a number of
-      different ways of achieving this.
+      With the exception of web pages which use WOFF fonts and either supply
+      them or link to google to download them, web pages have traditionally
+      suggested a list of preferred font family names if they cared (e.g.
+      Times New Roman, Serif). There are many reasons why people may wish to
+      have pages which specify a  preferred font use a different font, or
+      prefer specific fonts in Monospace or Sans or Serif. As you will expect,
+      there a number of different ways of achieving this.
     </para>
 
     <bridgehead renderas="sect3" id="fontconfig-user-docs"