Add parameter to reparent windows instead of killing them when closing a container

Necessary because when windows are unmapped, they are not necessary to
be killed (an application can unmap it temporarily).

src/cmdparse.y

@@ -314,11 +314,11 @@ kill:
         printf("killing!\n");
         /* check if the match is empty, not if the result is empty */
         if (match_is_empty(&current_match))
-            tree_close(focused);
+            tree_close(focused, true);
         else {
             TAILQ_FOREACH(current, &owindows, owindows) {
                 printf("matching: %p / %s\n", current->con, current->con->name);
-                tree_close(current->con);
+                tree_close(current->con, true);
             }
         }