Move all types/prototypes from cogl.h -> cogl[1]-context.h

So we can get to the point where cogl.h is merely an aggregation of
header includes for the 1.x api this moves all the function prototypes
and type definitions into a cogl-context.h and a new cogl1-context.h.

Ideally no code internally should ever need to include cogl.h as it just
represents the public facing header for accessing the 1.x api which
should only be used by Clutter.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

cogl/cogl-attribute-buffer.h

@@ -31,6 +31,11 @@
 #ifndef __COGL_ATTRIBUTE_BUFFER_H__
 #define __COGL_ATTRIBUTE_BUFFER_H__
 
+/* We forward declare the CoglAttributeBuffer type here to avoid some circular
+ * dependency issues with the following headers.
+ */
+typedef struct _CoglAttributeBuffer CoglAttributeBuffer;
+
 #include <cogl/cogl-context.h>
 
 G_BEGIN_DECLS
@@ -43,8 +48,6 @@ G_BEGIN_DECLS
  * FIXME
  */
 
-typedef struct _CoglAttributeBuffer	      CoglAttributeBuffer;
-
 /**
  * cogl_attribute_buffer_new:
  * @context: A #CoglContext