renderer: introduce destroy callback

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
diff --git a/src/compositor-wayland.c b/src/compositor-wayland.c
index 167fce6..0a3df03 100644
--- a/src/compositor-wayland.c
+++ b/src/compositor-wayland.c
@@ -612,7 +612,7 @@
 static void
 wayland_destroy(struct weston_compositor *ec)
 {
-	gl_renderer_destroy(ec);
+	ec->renderer->destroy(ec);
 
 	weston_compositor_shutdown(ec);
 
@@ -686,7 +686,7 @@
 	return &c->base;
 
 err_gl:
-	gl_renderer_destroy(&c->base);
+	c->base.renderer->destroy(&c->base);
 err_display:
 	wl_display_disconnect(c->parent.wl_display);
 err_compositor: