Outdated Rand crate makes it hard to replace Impl

[domenukk]

We're using lain in an example for LibAFL, a fuzzing library that supports multiple faster (non-cryptographic) random implementations, but we are unable to update our rand crate dependency, as it breaks with Lain's version, see AFLplusplus/LibAFL#327.
As the rand API, as far as I can tell, did not have any drastic changes, maybe you can update it at some point. Thanks