fix code generator for this case:

if (foo) {
  with (bar)
    if (baz)
      x();
} else y();

(the compressor removes the brackets since the consequent consists of a
single statement, but the codegen must include the brackets because
otherwise the `else` would refer to the inner `if`)

lib/output.js

@@ -611,10 +611,7 @@ function OutputStream(options) {
                 }
                 b = b.alternative;
             }
-            else if (b instanceof AST_While
-                     || b instanceof AST_Do
-                     || b instanceof AST_For
-                     || b instanceof AST_ForIn) {
+            else if (b instanceof AST_StatementWithBody) {
                 b = b.body;
             }
             else break;