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/dead-code.js

@@ -131,3 +131,19 @@ try_catch_finally: {
         "1",
     ]
 }
+
+accessor: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        ({
+            get a() {},
+            set a(v){
+                this.b = 2;
+            },
+            b: 1
+        });
+    }
+    expect: {}
+}