eval function callable

If I type
```js
println(eval("2 + 2"))
```
Oh Noes say Eval can be Harmful.
But if type
```js
a = eval
println(a("2 + 2"))
```
Then I get out 4. So clearly I can use eval without an error which is a BIG PROBLEM.

Start by reproducing both snippets in the live editor and locate the code that restricts direct eval calls. Trace how assigning eval to a variable bypasses that restriction. Done means the direct and aliased forms are handled consistently, with tests covering both examples.

Written by the indexing model from the issue text.