numEncoding `None` throws a little _too_ often

[JohanWiltink]

Under numEncoding None it is not even possible to pass numbers to functions that do not evaluate their arguments. It is possible to pass JS values other than Number, but passing a Number will make fromInt throw.

fromInt should just pass the value unmodified.

Numeric literals in code should be handled in the parser; in numEncoding None they should be valid identifier names, and handled as such. cf. #20