Remove a hard coded version number

was r11544.

chapter06/libffi.xml

@@ -50,7 +50,7 @@
 
     <para>修改 Makefile ，将头文件安装到标准的
     <filename class="directory">/usr/include</filename> 目录，而不是
-    <filename class="directory">/usr/lib/libffi-3.2.1/include</filename>。</para>
+    <filename class="directory">/usr/lib/libffi-&libffi-version;/include</filename>。</para>
 
 <screen><userinput remap="pre">sed -e '/^includesdir/ s/$(libdir).*$/$(includedir)/' \
     -i include/Makefile.in