Non-standard: Remove features included in ES6

This removes the following items from the non-standard table which are
now in ECMAScript 6:
* function statement
* function "name" property (this has been added to the ES6 table)
* `__proto__`
* const, let
* RegExp "y" flag
* most of the String HTML methods
* String#substr
* octal

Closes #150.