Correct tag hierarchy, to allow for table-of-contents entries.

docs/usermanual-ch01.xml

-<sect1 id="what-is-harfbuzz">
+<chapter id="what-is-harfbuzz">
   <title>What is Harfbuzz?</title>
   <para>
     Harfbuzz is a <emphasis>text shaping engine</emphasis>. It solves
     the problem of selecting and positioning glyphs from a font given a
     Unicode string.
   </para>
-  <sect2 id="why-do-i-need-it">
+  <section id="why-do-i-need-it">
     <title>Why do I need it?</title>
     <para>
       Text shaping is an integral part of preparing text for display. It
@@ -99,8 +99,8 @@
       rest of this manual, we are going to assume that you are the
       implementor of a text layout engine.
     </para>
-  </sect2>
-  <sect2 id="why-is-it-called-harfbuzz">
+  </section>
+  <section id="why-is-it-called-harfbuzz">
     <title>Why is it called Harfbuzz?</title>
     <para>
       Harfbuzz began its life as text shaping code within the FreeType
@@ -111,5 +111,5 @@
       engine for OpenType fonts - &quot;Harfbuzz&quot; is the Persian
       for &quot;open type&quot;.
     </para>
-  </sect2>
-</sect1>
\ No newline at end of file
+  </section>
+</chapter>
\ No newline at end of file

docs/usermanual-ch02.xml

-<sect1 id="hello-harfbuzz">
+<chapter id="hello-harfbuzz">
   <title>Hello, Harfbuzz</title>
   <para>
     Here's the simplest Harfbuzz that can possibly work. We will improve
@@ -90,7 +90,7 @@
   hb_buffer_destroy(buf);
   hb_font_destroy(hb_ft_font);
 </programlisting>
-  <sect2 id="what-harfbuzz-doesnt-do">
+  <section id="what-harfbuzz-doesnt-do">
     <title>What Harfbuzz doesn't do</title>
     <para>
       The code above will take a UTF8 string, shape it, and give you the
@@ -179,5 +179,5 @@ ABC אבג DEF
       Harfbuzz's API to refine that example and improve our text shaping
       capabilities.
     </para>
-  </sect2>
-</sect1>
\ No newline at end of file
+  </section>
+</chapter>
\ No newline at end of file

docs/usermanual-ch03.xml

-<sect1 id="buffers-language-script-and-direction">
+<chapter id="buffers-language-script-and-direction">
   <title>Buffers, language, script and direction</title>
   <para>
     The input to Harfbuzz is a series of Unicode characters, stored in a
@@ -6,7 +6,7 @@
     the text that we want and then customize the properties of the
     buffer.
   </para>
-  <sect2 id="creating-and-destroying-buffers">
+  <section id="creating-and-destroying-buffers">
     <title>Creating and destroying buffers</title>
     <para>
       As we saw in our initial example, a buffer is created and
@@ -49,8 +49,8 @@ void somefunc(hb_buffer_t *buffer) {
       throw away the string in the buffer but keep the options, you can
       instead call <literal>hb_buffer_clear_contents(buffer)</literal>.
     </para>
-  </sect2>
-  <sect2 id="adding-text-to-the-buffer">
+  </section>
+  <section id="adding-text-to-the-buffer">
     <title>Adding text to the buffer</title>
     <para>
       Now we have a brand new Harfbuzz buffer. Let's start filling it
@@ -58,20 +58,20 @@ void somefunc(hb_buffer_t *buffer) {
       of Unicode codepoints, but your input string is probably in one of
       the standard Unicode character encodings (UTF-8, UTF-16, UTF-3 )
     </para>
-  </sect2>
-  <sect2 id="setting-buffer-properties">
+  </section>
+  <section id="setting-buffer-properties">
     <title>Setting buffer properties</title>
     <para>
     </para>
-  </sect2>
-  <sect2 id="what-about-the-other-scripts">
+  </section>
+  <section id="what-about-the-other-scripts">
     <title>What about the other scripts?</title>
     <para>
     </para>
-  </sect2>
-  <sect2 id="customizing-unicode-functions">
+  </section>
+  <section id="customizing-unicode-functions">
     <title>Customizing Unicode functions</title>
     <para>
     </para>
-  </sect2>
-</sect1>
\ No newline at end of file
+  </section>
+</chapter>
\ No newline at end of file

docs/usermanual-ch04.xml

-<sect1 id="fonts-and-faces">
+<chapter id="fonts-and-faces">
   <title>Fonts and faces</title>
-  <sect2 id="using-freetype">
+  <section id="using-freetype">
     <title>Using FreeType</title>
     <para>
     </para>
-  </sect2>
-  <sect2 id="using-harfbuzzs-native-opentype-implementation">
+  </section>
+  <section id="using-harfbuzzs-native-opentype-implementation">
     <title>Using Harfbuzz's native OpenType implementation</title>
     <para>
     </para>
-  </sect2>
-  <sect2 id="using-your-own-font-functions">
+  </section>
+  <section id="using-your-own-font-functions">
     <title>Using your own font functions</title>
     <para>
     </para>
-  </sect2>
-</sect1>
\ No newline at end of file
+  </section>
+</chapter>
\ No newline at end of file

docs/usermanual-ch05.xml

-<sect1 id="shaping-and-shape-plans">
+<chapter id="shaping-and-shape-plans">
   <title>Shaping and shape plans</title>
-  <sect2 id="opentype-features">
+  <section id="opentype-features">
     <title>OpenType features</title>
     <para>
     </para>
-  </sect2>
-  <sect2 id="plans-and-caching">
+  </section>
+  <section id="plans-and-caching">
     <title>Plans and caching</title>
     <para>
     </para>
-  </sect2>
-</sect1>
\ No newline at end of file
+  </section>
+</chapter>
\ No newline at end of file