evas/evas3d: set gl backened forcely in the examples

Right now, evas 3d doesn't support software renderer,
we set the gl backened forcely.

src/examples/evas/evas-3d-cube.c

@@ -227,6 +227,9 @@ _scene_setup(Scene_Data *data)
 int
 main(void)
 {
+   //Unless Evas 3D supports Software renderer, we set gl backened forcely.
+   setenv("ECORE_EVAS_ENGINE", "opengl_x11", 1);
+
    Scene_Data data;
 
    if (!ecore_evas_init()) return 0;

src/examples/evas/evas-3d-cube2.c

@@ -292,6 +292,9 @@ _scene_setup(Scene_Data *data)
 int
 main(void)
 {
+   //Unless Evas 3D supports Software renderer, we set gl backened forcely.
+   setenv("ECORE_EVAS_ENGINE", "opengl_x11", 1);
+
    Scene_Data data;
 
    if (!ecore_evas_init()) return 0;

src/examples/evas/evas-3d-md2.c

@@ -59,6 +59,9 @@ _on_canvas_resize(Ecore_Evas *ee)
 int
 main(void)
 {
+   //Unless Evas 3D supports Software renderer, we set gl backened forcely.
+   setenv("ECORE_EVAS_ENGINE", "opengl_x11", 1);
+
    if (!ecore_evas_init()) return 0;
 
    ecore_evas = ecore_evas_new(NULL, 10, 10, WIDTH, HEIGHT, NULL);

src/examples/evas/evas-3d-pick.c

@@ -295,6 +295,9 @@ _on_mouse_down(void	    *data EINA_UNUSED,
 int
 main(void)
 {
+   //Unless Evas 3D supports Software renderer, we set gl backened forcely.
+   setenv("ECORE_EVAS_ENGINE", "opengl_x11", 1);
+
    if (!ecore_evas_init())
      return 0;
 

src/examples/evas/evas-3d-proxy.c

@@ -255,6 +255,9 @@ _scene_setup(Scene_Data *data)
 int
 main(void)
 {
+   //Unless Evas 3D supports Software renderer, we set gl backened forcely.
+   setenv("ECORE_EVAS_ENGINE", "opengl_x11", 1);
+
    Scene_Data data;
 
    if (!ecore_evas_init())