fix bugs with getter/setter (#1926)

- `reduce_vars`
- `side_effects`
- property access for object
- `AST_SymbolAccessor` as key names

enhance `test/ufuzz.js`
- add object getter & setter
  - property assignment to setter
  - avoid infinite recursion in setter
- fix & adjust assignment operators
  - 50% `=`
  - 25% `+=`
  - 2.5% each for the rest
- avoid "Invalid array length"
- fix `console.log()`
  - bypass getter
  - curb recursive reference
- deprecate `-E`, always report runtime errors

test/compress/pure_getters.js

@@ -119,3 +119,62 @@ chained: {
         a.b.c;
     }
 }
+
+impure_getter_1: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).a;
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).b;
+    }
+    expect: {
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).a;
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).b;
+    }
+    expect_stdout: "1"
+}
+
+impure_getter_2: {
+    options = {
+        pure_getters: true,
+        side_effects: true,
+    }
+    input: {
+        // will produce incorrect output because getter is not pure
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).a;
+        ({
+            get a() {
+                console.log(1);
+            },
+            b: 1
+        }).b;
+    }
+    expect: {}
+}