validate against multiple parents on AST_Node (#4032)

- fix related issues in `global_defs`, `ie8` & `reduce_vars`

test/compress/global_defs.js

@@ -12,6 +12,20 @@ must_replace: {
     }
 }
 
+repeated_nodes: {
+    options = {
+        global_defs: {
+            "@N": "rand()",
+        },
+    }
+    input: {
+        console.log(N, N);
+    }
+    expect: {
+        console.log(rand(), rand());
+    }
+}
+
 keyword: {
     options = {
         global_defs: {

test/compress/ie8.js

@@ -2691,3 +2691,26 @@ issue_4028: {
     }
     expect_stdout: "string"
 }
+
+issue_2737: {
+    options = {
+        ie8: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            a();
+        })(function f() {
+            console.log(typeof f);
+        });
+    }
+    expect: {
+        (function(a) {
+            a();
+        })(function f() {
+            console.log(typeof f);
+        });
+    }
+    expect_stdout: "function"
+}