Remove non-standard properties from Function.prototype

[saghul]

Closes: #713

[bnoordhuis]

So... I'm acutely aware they're non-standard but they're also pretty useful.

[saghul]

I have no strong opinion TBH.

I made the PR in case we concluded we wanted them out.

For documentation purposes: what use do you have for them?

[bnoordhuis]

I guess it's a little debug tool because it tells you where a function object comes from.

[saghul]

I'm ok with having it.