multilib: Update host kernel requirement for multilib

Switch to the new kernel config rendering infrastructure.  Remove the
"IA32 a.out support" which is already removed and was completely useless
for multilib even before the removal.  Mention the new "IA32 emulation
disabled by default" option.  Separate mx32 and m32 kernel
configuration.  Fix the consequences building a multilib when lacking
the corresponding kernel feature.

chapter02/hostreqs.xml

@@ -276,24 +276,34 @@ EOF
 
 bash version-check.sh</userinput></screen>
 
-    <para arch="ml_32,ml_x32,ml_all">
-      Building multilib support requires the kernel of the host system
-      to have 32-bit emulation support included.
+    <para arch="ml_32,ml_all">
+      Building the m32 multilib support requires the kernel of the host
+      system to have the 32-bit emulation support included:
     </para>
-<screen arch="ml_32,ml_x32,ml_all">Binary Emulations  ---&gt;
-    [*] IA32 Emulation
-    &lt;M&gt;   IA32 a.out support
-    [*] x32 ABI for 64-bit mode
-</screen>
 
-    <para arch="ml_32,ml_x32,ml_all">The option 'IA32 a.out support' is
-      optional. In case your kernel does not have 'x32 ABI for 64-bit mode'
-      enabled but only 'IA32 Emulation', you can continue to build your
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
+      href="../chapter10/kernel/multilib-32.xml"/>
+
+    <para arch="ml_x32,ml_all">
+      Building the mx32 multilib support requires the kernel of the host
+      system to have the x32 ABI support included:
+    </para>
+
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
+      href="../chapter10/kernel/multilib-x32.xml"/>
+
+    <para arch="ml_all">
+      In case your kernel does not have the x32 ABI support enabled but
+      only the 32-bit emulation support, you can continue to build your
       system but you have to leave out any sections showing instructions
-      for building x32 objects. If neither 'IA32 Emulation' nor 
-      'x32 ABI for 64-bit mode' is enabled, you will run in errors 
-      latest when building <application>glibc</application> in Chapter 6,
-      so an upgrade of your host system kernel is required.
+      for building x32 objects, vice versa.
+    </para>
+
+    <para arch="ml_32,ml_x32,ml_all">
+      If the kernel feature required by a multilib is not enabled,
+      building the multilib for a package in Chapter 8 may either fail
+      immediately, or cause hidden breakages because autoconf cannot
+      probe the system features properly.
     </para>
     
   </sect2>

chapter10/kernel/multilib-32.toml

@@ -0,0 +1,3 @@
+IA32_EMULATION='*'
+IA32_EMULATION_DEFAULT_DISABLED=' '
+arch='ml_32,ml_all'

chapter10/kernel/multilib-32.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE note PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<!-- Automatically generated by kernel-config.py
+     DO NOT EDIT! -->
+<screen role="nodump" arch="ml_32,ml_all"><emphasis role='blue'>B</emphasis>inary Emulations ---&gt;
+  [*] <emphasis role='blue'>I</emphasis>A32 Emulation                                            [IA32_EMULATION]
+  [ ]   <emphasis role='blue'>I</emphasis>A32 emulation disabled by default     [IA32_EMULATION_DEFAULT_DISABLED]</screen>

chapter10/kernel/multilib-x32.toml

@@ -0,0 +1,2 @@
+X86_X32_ABI='*'
+arch='ml_x32,ml_all'

chapter10/kernel/multilib-x32.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE note PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<!-- Automatically generated by kernel-config.py
+     DO NOT EDIT! -->
+<screen role="nodump" arch="ml_x32,ml_all"><emphasis role='blue'>B</emphasis>inary Emulations ---&gt;
+  [*] <emphasis role='blue'>x</emphasis>32 ABI for 64-bit mode                                      [X86_X32_ABI]</screen>