shell-animation: add conf option in shell

Now we can choose zoom or fade in weston.ini
to fulfill and customize the user experence easier.

Signed-off-by: Juan Zhao <juan.j.zhao@intel.com>
diff --git a/src/compositor.h b/src/compositor.h
index 5cf4285..3722d32 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -594,6 +594,14 @@
 weston_zoom_run(struct weston_surface *surface, GLfloat start, GLfloat stop,
 		weston_zoom_done_func_t done, void *data);
 
+struct weston_fade;
+typedef	void (*weston_fade_done_func_t)(struct weston_fade *fade, void *data);
+
+struct weston_fade *
+weston_fade_run(struct weston_surface *surface,
+		weston_fade_done_func_t done, void *data);
+
+
 void
 weston_surface_set_color(struct weston_surface *surface,
 			 GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha);