Fix a few more list refcount issues

src/runtime/builtin_modules/builtins.cpp

@@ -451,13 +451,13 @@ Box* sorted(Box* obj, Box* cmp, Box* key, Box** args) {
     Box* reverse = args[0];
 
     BoxedList* rtn = new BoxedList();
-    KEEP_ALIVE(rtn);
+    AUTO_DECREF(rtn);
     for (Box* e : obj->pyElements()) {
         listAppendInternalStolen(rtn, e);
     }
 
     listSort(rtn, cmp, key, reverse);
-    return rtn;
+    return incref(rtn);
 }
 
 Box* isinstance_func(Box* obj, Box* cls) {

src/runtime/list.cpp

@@ -889,6 +889,7 @@ public:
     PyCmpComparer(Box* cmp) : cmp(cmp) {}
     bool operator()(Box* lhs, Box* rhs) {
         Box* r = runtimeCallInternal<CXX, NOT_REWRITABLE>(cmp, NULL, ArgPassSpec(2), lhs, rhs, NULL, NULL, NULL);
+        AUTO_DECREF(r);
         if (!PyInt_Check(r))
             raiseExcHelper(TypeError, "comparison function must return int, not %.200s", r->cls->tp_name);
         return static_cast<BoxedInt*>(r)->n < 0;