Handled Ruby's exceptions correctly

[irxground]

VM::raise_ex is a dangerous function and should be used carefully

Rust has a drop function to release memory, etc. This internal implementation is a feature called unwind. Ruby, on the other hand, uses longjump as an exception. Rust's drop function doesn't work properly when using two functions together. If you throw a Ruby exception in the middle of a Rust program, the following program will not be executed, so a memory leak may occur.

I introduced the unwrap_or_raise function and corrected so that drop will always be executed before a Ruby exception occurs.

[Hywan]

Thanks for the PR! It was clearly on my radar, so thank you for doing it.

I'll review the PR as soon as possible. Everything looks good to me so far.

[irxground]

I'm sorry. I missed one place.

[Hywan]

bors try

[Hywan]

LGTM! Thank you very much :-).