Compatibility with frozen Object prototype

[norbertsuski]

• Freezing the global Object prototype is one of the best ways to defend against Prototype Pollution attacks
• Doing this changes all properties of the Object prototype to become non-writable
• JavaScript does not allow you to use the "=" assignment operator to "shadow" any inherited, non-writable object properties -- in particular, the "toString" property
• The correct way to do this is to use the Object.defineProperty() syntax instead