Fully integrates CoglMaterial throughout the rest of Cogl

This glues CoglMaterial in as the fundamental way that Cogl describes how to
fill in geometry.

It adds cogl_set_source (), which is used to set the material which will be
used by all subsequent drawing functions

It adds cogl_set_source_texture as a convenience for setting up a default
material with a single texture layer, and cogl_set_source_color is now also
a convenience for setting up a material with a solid fill.

"drawing functions" include, cogl_rectangle, cogl_texture_rectangle,
cogl_texture_multiple_rectangles, cogl_texture_polygon (though the
cogl_texture_* funcs have been renamed; see below for details),
cogl_path_fill/stroke and cogl_vertex_buffer_draw*.

cogl_texture_rectangle, cogl_texture_multiple_rectangles and
cogl_texture_polygon no longer take a texture handle; instead the current
source material is referenced. The functions have also been renamed to:
cogl_rectangle_with_texture_coords, cogl_rectangles_with_texture_coords
and cogl_polygon respectivly.

Most code that previously did:
  cogl_texture_rectangle (tex_handle, x, y,...);
needs to be changed to now do:
  cogl_set_source_texture (tex_handle);
  cogl_rectangle_with_texture_coords (x, y,....);

In the less likely case where you were blending your source texture with a color
like:
  cogl_set_source_color4ub (r,g,b,a); /* where r,g,b,a isn't just white */
  cogl_texture_rectangle (tex_handle, x, y,...);
you will need your own material to do that:
  mat = cogl_material_new ();
  cogl_material_set_color4ub (r,g,b,a);
  cogl_material_set_layer (mat, 0, tex_handle));
  cogl_set_source_material (mat);

Code that uses the texture coordinates, 0, 0, 1, 1 don't need to use
cog_rectangle_with_texure_coords since these are the coordinates that
cogl_rectangle will use.

For cogl_texture_polygon; as well as dropping the texture handle, the
n_vertices and vertices arguments were transposed for consistency. So
code previously written as:
  cogl_texture_polygon (tex_handle, 3, verts, TRUE);
need to be written as:
  cogl_set_source_texture (tex_handle);
  cogl_polygon (verts, 3, TRUE);

All of the unit tests have been updated to now use the material API and
test-cogl-material has been renamed to test-cogl-multitexture since any
textured quad is now technically a test of CoglMaterial but this test
specifically creates a material with multiple texture layers.

Note: The GLES backend has not been updated yet; that will be done in a
following commit.

clutter/clutter-main.c

@@ -1157,18 +1157,6 @@ clutter_init_real (GError **error)
   if (!_clutter_backend_post_parse (backend, error))
     return CLUTTER_INIT_ERROR_BACKEND;
 
-  /*
-   * Resolution requires display to be open, so can only be queried after
-   * the post_parse hooks run.
-   */
-  ctx->font_map = COGL_PANGO_FONT_MAP (cogl_pango_font_map_new ());
-
-  resolution = clutter_backend_get_resolution (ctx->backend);
-  cogl_pango_font_map_set_resolution (ctx->font_map, resolution);
-  cogl_pango_font_map_set_use_mipmapping (ctx->font_map, TRUE);
-
-  clutter_text_direction = clutter_get_text_direction ();
-
   /* Stage will give us a GL Context etc */
   stage = clutter_stage_get_default ();
   if (!stage)
@@ -1201,6 +1189,21 @@ clutter_init_real (GError **error)
    * start issueing cogl commands
   */
 
+  /*
+   * Resolution requires display to be open, so can only be queried after
+   * the post_parse hooks run.
+   *
+   * NB: cogl_pango requires a Cogl context.
+   */
+  ctx->font_map = COGL_PANGO_FONT_MAP (cogl_pango_font_map_new ());
+
+  resolution = clutter_backend_get_resolution (ctx->backend);
+  cogl_pango_font_map_set_resolution (ctx->font_map, resolution);
+  cogl_pango_font_map_set_use_mipmapping (ctx->font_map, TRUE);
+
+  clutter_text_direction = clutter_get_text_direction ();
+
+
   /* Figure out framebuffer masks used for pick */
   cogl_get_bitmasks (&ctx->fb_r_mask, &ctx->fb_g_mask, &ctx->fb_b_mask, NULL);