Tracking Issue: export attributes

[Shizcow]

As mentioned in this reddit comment, if a patch implementation from an external library has unsafe code then patchable functions should require unsafe.

As this crate already exports some information alongside functions (module path, signature), I'd like to move in the direction of adding more attributes. unsafe would be one. I have yet to come up with others.

For passers by: suggestions on other attributes are highly appreciated.