[ES6] Implemented parse for export Name from Module variants. (#1701)

- add `AST_Export` new variants output
- add tests to `test/compress/`
- update `$propdoc` of `AST_Export` ("exported_names" & "module_name")
- add tests for `export ...  as ...` variants

lib/output.js

@@ -1277,11 +1277,37 @@ function OutputStream(options) {
             output.print("default");
             output.space();
         }
-        if (self.exported_value) {
+        if (self.exported_names) {
+            output.space();
+
+            if (self.exported_names.length === 1 && self.exported_names[0].name.name === "*") {
+                self.exported_names[0].print(output);
+            } else {
+                output.print("{");
+                self.exported_names.forEach(function (name_import, i) {
+                    output.space();
+                    name_import.print(output);
+                    if (i < self.exported_names.length - 1) {
+                        output.print(",");
+                        output.space();
+                    }
+                });
+                output.space();
+                output.print("}");
+            }
+            output.space();
+        }
+        else if (self.exported_value) {
             self.exported_value.print(output);
         } else if (self.exported_definition) {
             self.exported_definition.print(output);
         }
+        if (self.module_name) {
+            output.space();
+            output.print("from");
+            output.space();
+            self.module_name.print(output);
+        }
         output.semicolon();
     });