Touch up controller logic to handle nested items well.

The test in the previous commit now passes

full-tests/nested-items2.rs

@@ -0,0 +1,24 @@
+// this should all get deleted in a single swoop *and* not panic about it
+/// ~REQUIRE-DELETED l1
+mod l1 {
+    mod l2 {
+        mod l3 {
+            mod l4{
+                mod l5 {
+                    fn foo(){}
+                    fn bar(){}
+                    mod l6 {
+                        fn x1(){}
+                    }
+                    fn x2(){}
+                }
+            }
+            mod l4_2 {
+                fn y(){}
+            }
+        }
+    }
+    fn x8(){}
+}
+/// ~MINIMIZE-ROOT main
+fn main(){}