newString(len) has off-by-one error

[luked99]

I think newString() might have an off-by-one error.

var s = newString(0)
s[0] = 'a'   # this works fine!
s[1] = 'b'   # this fails as you might expect

And so-on for larger values. I'm not sure to what extent this is a bug, or by design.

[Araq]

It's by design but there is already an RFC to change that. Closing.

[yglukhov]

#5596