Handle window pre visibility change event

Handle window pre visibility change event

When getting ECORE_WL_WINDOW_VISIBILITY_TYPE_PRE_UNOBSCURED event,
an application is changed to the resume state.
This patch is for backward compatibility.

+---------------+--------------------------------------------------+
| Tizen version | Window state                                     |
+---------------+--------------------------------------------------+
| 2.x           | Pause -> Resume(visibility change) -> Render     |
+---------------+--------------------------------------------------+
| 3.0 (before)  | Pause -> Render -> Resume(visibility change)     |
+---------------+--------------------------------------------------+
| 3.0 (after)   | Pause -> Resume(pre visibility change) -> Render |
+---------------+--------------------------------------------------+

Change-Id: Ife2da19a8675a8cce8beb1392720f785c40e569f
Signed-off-by: Hwankyu Jhun <h.jhun@samsung.com>