Rule: ie-catch-leak

The `ie-catch-leak` rule disallows a catch clause parameter with the same name as a variable in the outer scope. IE 8 and earlier will leak the catch clause parameter into the outer scope and overwrite the outer scope variable value.

```js
var err = "x";

try {
    throw "problem";
} catch (err) {

}

console.log(err)    // err is 'problem', not 'x'
```

This rule matches JSHint rule W002.