whatsnew: Update for GCC 13.1

And let's discourage reusing scripts.

chapter01/whatsnew.xml

@@ -11,13 +11,25 @@
 
   <title>What's new since the last release</title>
 
-  <para>In the 11.3 release, <parameter>--enable-default-pie</parameter>
-  and <parameter>--enable-default-ssp</parameter> are enabled for GCC.
-  These techniques can mitigate some malicious attacks, but they do not provide
-  perfect security.  Note that some textbooks assume these options are
-  disabled, so that if you run examples from such a textbook on an LFS system,
-  you may need to disable PIE and SSP with the GCC options
-  <parameter>-fno-pie -no-pie -fno-stack-protection</parameter>.</para>
+  <caution>
+    <para>
+      During a development cycle of LFS, the instructions in the book is
+      often modified to adapt for a package update or take the advantage of
+      new features from updated packages.  Mixing up the instructions of
+      different versions of the LFS book can cause subtle breakages.  This
+      kind of issue is generally a result from reusing some script created
+      for a prior LFS release.  Such a reuse is strongly discouraged.  If
+      you are reusing scripts for a prior LFS release for any reason, you'll
+      need to be very careful to update the scripts to match current version
+      of the LFS book.
+    </para>
+  </caution>
+
+  <para>In the 11.4 release, <parameter>--disable-fixincludes</parameter>
+  is set for GCC.  It's a configure switch newly added in GCC 13.1 to
+  prevent GCC from <quote>fixing</quote> the system headers.  Such a
+  <quote>fix</quote> is unnecessary for a modern Linux system and may cause
+  issues if a package is updated after installing GCC.</para>
 
   <para>Here is a list of the packages updated since the previous
   release of LFS.</para>