handle: A Range that handles an Exception

When a Exception occurs inside a range chaining the whole chain dies usually. The Handle range fixes that, as it catches a defined exception and calls an user defined handler on it.
You don't have to change this, as it's a matter of formatting preference, but I think that it's better not to have the braces here, because they're unnecessary. C++ is annoying and requires them for try and catch blocks, but D doesn't.