Use Node.js' util module when running in Node.

[lddubeau]

Once upon a time salve was able to switch automatically between the util module provided by Node and a fake util module that could have been used in the browser. This was done to support calls util.inspect in debugging code, and hiding the fact that util.inspect does not exist in browsers.

When we moved to webpack to combine the sources, we lost this capability. Now, only the fake util.inspect is used, no matter whether we are running in Node or not. It would be nice to recover the original capability.

[lddubeau]

We've lived over a year without this capability and did not miss it, so let's close this.