GLView: Add API to get the Evas_GL

Before screaming "don't expose this", here's the reasoning:
There will be a few new APIs in evas-gl (support pbuffer, ...)
that require a pointer to the Evas_GL to be called. So, instead
of exposing each and every one of these evas gl functions in
a dummy wrapper in elm_glview, we just give access to the real
pointer.
GLView will always be a wrapper around evas_gl, because that's
what it is by definition.

legacy/elementary/src/lib/elm_glview.c

@@ -417,6 +417,12 @@ _elm_glview_changed_set(Eo *obj, Elm_Glview_Data *sd)
        ecore_idle_enterer_before_add((Ecore_Task_Cb)_render_cb, obj);
 }
 
+EOLIAN static Evas_GL *
+_elm_glview_evas_gl_get(Eo *obj EINA_UNUSED, Elm_Glview_Data *sd)
+{
+   return sd->evasgl;
+}
+
 static void
 _elm_glview_class_constructor(Eo_Class *klass)
 {

legacy/elementary/src/lib/elm_glview.eo

@@ -162,6 +162,23 @@ class Elm_Glview (Elm_Widget)
             return: Evas_GL_API *;
          }
       }
+      evas_gl {
+         get {
+            /*@
+            Get the internal Evas GL attached to this view.
+
+            @note The returned Evas_GL must not be destroyed as it is still owned
+            by the view. But this pointer can be used then to call all the evas_gl_
+            functions.
+
+            @since 1.12
+
+            @return The Evas_GL used by this GLView.
+
+            @ingroup GLView */
+            return: Evas_GL *;
+         }
+      }
    }
    implements {
       class.constructor;