compositor: Add destroy signal of E_Surface

compositor: Add destroy signal of E_Surface

As a thin wrapper of ds_surface, E_Surface is bound to ds_surface.
That is, E_Surface become inert if ds_surface is destroyed.

E_Surface should be separated from the life cycle of E_Client, but it's
hard to do it for now because E_Surface is tightly coupled with
E_Client - It provides many functionalities related to comp_data member
variable of E_Client.

So, let the destroy signal of E_Surface emit when the destroy signal of
ds_surface is emitted.

Change-Id: Ie5cf65a20c9765e78b8d1caecfd20883b464357f