tests: Use the portable cogl wrappers for GLSL builtins

Instead of directly using the GLSL names for the builtins in the
shaders for test-shader and test-pick, this makes it use the Cogl
wrapper names instead. That way it will be portable to GLES2 as well.

Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>

tests/conform/test-pick.c

@@ -55,8 +55,8 @@ shader_paint (ClutterEffect           *effect,
     "uniform float step;\n"
     "void main (void)\n"
     "{\n"
-    "  gl_FragColor = texture2D(tex, vec2 (gl_TexCoord[0].s + step,\n"
-    "                                      gl_TexCoord[0].t));\n"
+    "  cogl_color_out = texture2D(tex, vec2 (cogl_tex_coord_in[0].s + step,\n"
+    "                                        cogl_tex_coord_in[0].t));\n"
     "}\n");
 
   tex_width = clutter_actor_get_width (actor);

tests/interactive/test-shader.c

@@ -36,8 +36,7 @@ typedef struct
  * correctly).
  */
 #define FRAGMENT_SHADER_END                    \
-      "  gl_FragColor = color;"    \
-      "  gl_FragColor = gl_FragColor * cogl_color_in;" \
+      "  cogl_color_out = color * cogl_color_in;" \
       "}"
 
 static ShaderSource shaders[]=