ExcpetionHandlingIterable no longer uses Unsafe.

It was an ugly hack before, and it's still an ugly hack, but now
it is an ugly hack that does not use the Unsafe. So a small
improvement.

Really though, we should do something about the fact that we expect
checked expceptions through the Iterable methods.
Merge pull request #1247 from chrisvest/excheption-rethrow-hack-without-unsafe

ExcpetionHandlingIterable no longer uses Unsafe.