Add notes about gobject-introspection

INSTALL.in

@@ -7,6 +7,8 @@ GTK+ requires the following packages:
    location as GTK+. GTK+ @GTK_VERSION@ requires at least GLib 2.23.6,
    Pango 1.20, ATK 1.29.2 and cairo 1.6.0.
 
+ - gobject-introspection 0.6.7 or newer.
+
  - The TIFF, PNG, and JPEG image loading libraries. You most
    likely have these installed on your system already. If not
    these libraries are available from:

README.in

@@ -41,6 +41,11 @@ Release notes for 2.20
   attribute of the <object>. Use gtk_buildable_get_name() instead of
   gtk_widget_get_name() to obtain the ID.
 
+* GTK+ now includes introspection data, as a consequence, it gained a
+  dependency on gobject-introspection. It is possible to build without
+  introspection by passing --disable-introspection to configure.
+
+
 Release notes for 2.18
 ======================
 

docs/reference/gtk/building.sgml

@@ -255,6 +255,13 @@ How to compile GTK+ itself
           drawing.
         </para>
       </listitem>
+      <listitem>
+	<para>
+	  <ulink url="http://live.gnome.org/GObjectIntrospection">gobject-introspection</ulink>
+          is a framework for making introspection data available to
+          language bindings.
+        </para>
+      </listitem>
       <listitem>
         <para>
           The <ulink url="http://www.freedesktop.org/wiki/Software/shared-mime-info">shared-mime-info</ulink> 
@@ -368,6 +375,9 @@ How to compile GTK+ itself
 	  <group>
 	    <arg>--with-gdktarget=[x11|win32|quartz|directfb]</arg>
 	  </group>
+          <group>
+	    <arg>--disable-introspection</arg>
+          </group>
 	</cmdsynopsis>
       </para>
 
@@ -580,7 +590,13 @@ How to compile GTK+ itself
           for the Linux framebuffer.
 	</para>
       </formalpara>
+      <formalpara>
+        <title><systemitem>--disable-introspection</systemitem></title>
 
+        <para>
+          Build without introspection support.
+        </para>
+      </formalpara>
     </refsect1>
 
 </refentry>