I don't think it makes too much of a difference if you're using `--exceptions:goto`, but might provides considerable boost if `--exceptions:setjmp` is used.
`--panics:on` allows the compiler to stop assuming that all procs can throw, as all `Defect` will then be compiled down into `quit()`. This should reduce the amount of `try-finally` pairs generated, which is "slow" for setjmp. With that said, not many code actually use the new destructors function nor `defer` so the perf gains might not be huge.
