cogl-buffer: add an abstract class around openGL's buffer objects

Buffer objects are cool! This abstracts the buffer API first introduced
by GL_ARB_vertex_buffer_object and then extended to other objects.

The coglBuffer abstract class is intended to be the base class of all
the buffer objects, letting the user map() buffers. If the underlying
implementation does not support buffer objects (or only support VBO but
not FBO for instance), fallback paths should be provided.

doc/reference/cogl/cogl-docs.xml.in

@@ -71,6 +71,27 @@
 
   </chapter>
 
+  <chapter>
+    <title>COGL experimental API</title>
+
+    <section id="cogl-experimental">
+      <title>About the experimental API</title>
+
+      <para>COGL has some experimental API developers are welcomed to play
+      with. The main drawback when using those is that there is no API
+      stability guarantee, functions flagged as experimental could be changed
+      or removed in future versions of the library. To use this experimental
+      API you will need to define
+      <literal>COGL_ENABLE_EXPERIMENTAL_API</literal> before including
+      <filename class="headerfile">&lt;clutter/clutter.h&gt;</filename> or
+      <filename class="headerfile">&lt;cogl/cogl.h&gt;</filename>.</para>
+
+    </section>
+
+    <xi:include href="xml/cogl-buffer.xml"/>
+
+  </chapter>
+
   <index>
     <title>Index of all symbols</title>
     <xi:include href="xml/api-index-full.xml"><xi:fallback /></xi:include>

doc/reference/cogl/cogl-sections.txt

@@ -472,3 +472,20 @@ CoglMaterialLayerType
 cogl_material_layer_get_type
 cogl_material_layer_get_texture
 </SECTION>
+
+<SECTION>
+<FILE>cogl-buffer</FILE>
+<TITLE>Buffers</TITLE>
+cogl_is_buffer
+cogl_buffer_get_size
+CoglBufferUsageHint
+cogl_buffer_set_usage_hint
+cogl_buffer_get_usage_hint
+CoglBufferUpdateHint
+cogl_buffer_set_update_hint
+cogl_buffer_get_update_hint
+CoglBufferAccess
+cogl_buffer_map
+cogl_buffer_unmap
+cogl_buffer_set_data
+</SECTION>