Fix building GLES 2 after the material branch merge

- In cogl-material.h it directly sets the values of the
  CoglMaterialLayerCombineFunc to some GL_* constants. However these
  aren't defined in GLES 2 beacuse it has no fixed function texture
  combining. Instead the CGL_* versions are now used. cogl-defines.h
  now sets these to either the GL_* version if it is available,
  otherwise it directly uses the number.

- Under GLES 2 cogl-material.c needs to access the CoglTexture struct
  so it needs to include cogl-texture-private.h

- There are now #define's in cogl-gles2-wrapper.h to remap the GL
  function names to the wrapper names. These are disabled in
  cogl-gles2-wrapper.c by defining COGL_GLES2_WRAPPER_NO_REMAP.

- Added missing wrappers for glLoadMatrixf and glMaterialfv.

- Renamed the TexEnvf wrapper to TexEnvi because the latter is used
  instead from the material API.

common/cogl-material.c

@@ -9,6 +9,7 @@
 #include "cogl-handle.h"
 
 #include "cogl-material-private.h"
+#include "cogl-texture-private.h"
 
 #include <glib.h>
 #include <string.h>
@@ -18,7 +19,7 @@
  */
 
 #ifdef HAVE_COGL_GLES2
-#define glAlphaFunc cogl_wrap_glAlphaFunc
+#include "../gles/cogl-gles2-wrapper.h"
 #endif
 
 static void _cogl_material_free (CoglMaterial *tex);

common/cogl-vertex-buffer.c

@@ -159,14 +159,7 @@
 
 #elif defined (HAVE_COGL_GLES2)
 
-#define glVertexPointer cogl_wrap_glVertexPointer
-#define glNormalPointer cogl_wrap_glNormalPointer
-#define glTexCoordPointer cogl_wrap_glTexCoordPointer
-#define glColorPointer cogl_wrap_glColorPointer
-#define glDrawArrays cogl_wrap_glDrawArrays
-
-#define glEnableClientState cogl_wrap_glEnableClientState
-#define glDisableClientState cogl_wrap_glDisableClientState
+#include "../gles/cogl-gles2-wrapper.h"
 
 #endif