Destructuring consistency fixes (#1417)

- Use AST_Destructuring for lhf assignment patterns
- Use AST_DefaultAssign for default assignments
- Add more checks for lhs expressions
- Add lots of testing
- Cleanup ast (e.g. remove default property)
- Fix #1402 based on a patch from @kzc
- Refine spread allowance in array destructring pattern
- Add destructuring AST tree checker

test/compress/try-catch.js

@@ -1,4 +1,7 @@
 catch_destructuring_with_sequence: {
+    beautify = {
+        ecma: 6
+    }
     input: {
         try {
             throw {};