Ruby hidden explicit_bzero() function exported.

Ruby's C implementation has its explicit_bzero() function but it never make the function available from the ruby land. I'll do that for you.

This library provides one method named String#explicit_bzero. Which is of course not very ruby-ish, I know, but best describes what is going on.

string.explicit_bzero() # => self

Cleanse the receiver. Raises FrozenError if the receiver is frozen.

Your ruby is too old. All Ruby since 2015 has this function.

I suspect that's possible. Not sure how though. Pull request much appreciated.