xlib: Implement lp_winsys::destroy.

src/gallium/winsys/xlib/xlib_llvmpipe.c

@@ -364,6 +364,13 @@ no_xm_dt:
 }
 
 
+static void
+xm_destroy( struct llvmpipe_winsys *ws )
+{
+   FREE(ws);
+}
+
+
 static struct llvmpipe_winsys *
 xlib_create_llvmpipe_winsys( void )
 {
@@ -373,6 +380,8 @@ xlib_create_llvmpipe_winsys( void )
    if (!ws)
       return NULL;
 
+   ws->base.destroy = xm_destroy;
+
    ws->base.is_displaytarget_format_supported = xm_is_displaytarget_format_supported;
 
    ws->base.displaytarget_create = xm_displaytarget_create;