man: add a new section for EFI variables

We should probably refer to them from other man pages
for programs which use them, since right now all refs are
in systemd-boot(7). But creating the section is a good step
anyway.

man/systemd-boot.xml

@@ -243,7 +243,7 @@
     UUID <literal>4a67b082-0a4c-41cf-b6c7-440b29bb8c4</literal>, for communication between the OS and the boot
     loader:</para>
 
-    <variablelist>
+    <variablelist class='efi-variables'>
       <varlistentry>
         <term><varname>LoaderBootCountPath</varname></term>
         <listitem><para>If boot counting is enabled, contains the path to the file in whose name the boot counters are

tools/make-directive-index.py

@@ -52,6 +52,16 @@ TEMPLATE = '''\
                 <variablelist id='environment-variables' />
         </refsect1>
 
+        <refsect1>
+                <title>EFI variables</title>
+
+                <para>EFI variables understood by
+                <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+                and other programs.</para>
+
+                <variablelist id='efi-variables' />
+        </refsect1>
+
         <refsect1>
                 <title>UDEV directives</title>