attribute: Split out GL specific code

As part of an on-going effort to enable non-opengl drivers for Cogl this
splits out the GL specific code in cogl-attribute.c into
cogl/driver/gl/cogl-attribute-gl.c

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

(cherry picked from commit 7e20c39c47fa176aa5062867ff273bc2c41a2f22)

cogl/driver/gl/cogl-attribute-gl-private.h

@@ -0,0 +1,44 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2012 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * Authors:
+ *   Robert Bragg <robert@linux.intel.com>
+ */
+
+#ifndef _COGL_ATTRIBUTE_GL_PRIVATE_H_
+#define _COGL_ATTRIBUTE_GL_PRIVATE_H_
+
+#include "cogl-types.h"
+#include "cogl-framebuffer.h"
+#include "cogl-attribute.h"
+#include "cogl-attribute-private.h"
+
+void
+_cogl_gl_flush_attributes_state (CoglFramebuffer *framebuffer,
+                                 CoglPipeline *pipeline,
+                                 CoglFlushLayerState *layers_state,
+                                 CoglDrawFlags flags,
+                                 CoglAttribute **attributes,
+                                 int n_attributes);
+
+#endif /* _COGL_ATTRIBUTE_GL_PRIVATE_H_ */