Added note that ed is optional

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@1119 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter06/ed-inst.xml

@@ -1,6 +1,11 @@
 <sect2>
 <title>Installation of Ed</title>
 
+<para>Ed is an optional package. The only program on a normal LFS system
+that uses ed is patch. But these days, ed patch files are quite rare in
+favour of the diff format patch files. So, if you personally have no
+need to use ed, you can skip it.</para>
+
 <para>Install Ed by running the following commands:</para>
 
 <para><screen><userinput>cp buf.c buf.c.backup &amp;&amp;</userinput>