lib: make sure console is writable

The code currently assumes that `console` is already writable, but
that's only if it was previously defined as writable. If it hasn't
already been defined then the default value is false.

PR-URL: #518
Reviewed-By: Seth Brenith <sethb@microsoft.com>
Reviewed-By: Jimmy Thomson <jithomso@microsoft.com>

Author: kfarnung

lib/internal/bootstrap/node.js

@@ -377,7 +377,8 @@
     Object.defineProperty(global, 'console', {
       configurable: true,
       enumerable: false,
-      value: wrappedConsole
+      value: wrappedConsole,
+      writable: true
     });
     setupInspector(originalConsole, wrappedConsole, CJSModule);
   }