standardizing Error.stack or equivalent

[Christian Plesner Hansen]

>     js> try { eval("eval('FAIL')"); } catch (x) { print(x.stack); }
>     @typein line 2 > eval line 1 > eval:1:1
>     @typein line 2 > eval:1:1
>     @typein:2:7

I'm unclear on what the problem is with nested evals -- you get
essentially the same information from v8:

js> try { eval("eval('FAIL')"); } catch (x) { console.log(x.stack); }
ReferenceError: FAIL is not defined
    at eval (eval at <anonymous> (eval at <anonymous> (repl:1:7)),
    <anonymous>:1:1)
    at eval (eval at <anonymous> (repl:1:7), <anonymous>:1:1)
    at repl:1:7


c