Let me know if there's something I should be doing differently as this is my first contribution to coffeescript.
I fixed the reported issue where a generated variable could clash with a user-defined one in a try/catch block.
I added a test for a few scenarios with different variable names for a try/catch, to confirm the fix and avoid regressions.
case to show it's required.
What's going on: inside of Coffee-generated closures, calling `super()`
is implicitly making use of `this` (or explicitly doing so if you look
at the output code), so we have to pass `this` through closures as if
`@` is being accessed within the closure. So, just add one more
condition to the list in `Closure::literalThis`
