Fix security issue in Chapter 8 glibc.

Add a sed to glibc in Chapter 8 to fix a critical security issue.

chapter01/changelog.xml

@@ -42,6 +42,16 @@
     <listitem revision="sysv"> or <listitem revision="systemd"> as
     appropriate for the entry or if needed the entire day's listitem.
     -->
+    <listitem>
+      <para>2021-08-20</para>
+      <itemizedlist>
+        <listitem>
+           <para>[bdubbs] - Add a sed to glibc in Chapter 8 to fix a 
+           critical security issue.</para>
+        </listitem>
+      </itemizedlist>
+    </listitem>
+
     <listitem>
       <para>2021-08-18</para>
       <itemizedlist>

chapter08/glibc.xml

@@ -43,6 +43,11 @@
   <sect2 role="installation">
     <title>Installation of Glibc</title>
 
+    <para>First, fix a security problem identified upstream:</para>
+
+    <screen><userinput remap="pre">sed -e '/NOTIFY_REMOVED)/s/)/ \&amp;\&amp; data.attr != NULL)/' \
+    -i sysdeps/unix/sysv/linux/mq_notify.c</userinput></screen> 
+
     <para>Some of the Glibc programs use the non-FHS compliant
     <filename class="directory">/var/db</filename> directory to store
     their runtime data. Apply the following patch to make such programs