efl_ui_win: Added frontbuffer mode.

efl_ui_win: Added frontbuffer mode.

Introduced new API:
- elm_win_use_frontbuffer_set(Evas_Object *obj, Eina_Bool
  use_frontbuffer) : setter of internal option.
- Eina_Bool elm_win_use_frontbuffer_get(Evas_Object *obj):
  getter of internal option.
- elm_win_frontbuffer_add()

When use_frontbuffer mode is set wayland engine uses frontbuffer
rendering mode on specified window.

Usage example:

   win = efl_add_ref(EFL_UI_WIN_CLASS, NULL,
                efl_ui_win_name_set(efl_added, "win-example"),
                efl_text_set(efl_added, "Elm_Win Example"),
                elm_win_use_frontbuffer_set(efl_added, EINA_TRUE));

   or:

   win = elm_win_frontbuffer_add(NULL, "win-example", "win-example", ELM_WIN_BASIC);

Change-Id: Ia1b06841f7ced23991d275ac09002bb89efa4fd2