Add Send impl for Module

[mcb2003]

This PR unsafely implements send for openmpt::module::Module. This is safe because the openmpt documentation states:

• You must ensure to only ever access a particular libopenmpt object from a
  single thread at a time.
• Consecutive accesses can happen from different threads.
• Different objects can be accessed concurrently from different threads.

So objects created by libopenmpt are Send, but not Sync.

I also fixed a few of the clippy warnings by E.G. replacing the deprecated x...y inclusive range operator with the newer x..=y.

I noticed that this repository hasn't been touched in quite a while, so I thaught I'd let you know I'd be happy to take over this project if you've lost interest / don't have the time any more. There are quite a few things I'd love to do to improve the API (better error handling, less copying when dealing with strings allocated on the libopenmpt side, etc). If you'd like to keep it though, no worries at all, just thaught I'd offer.

[mcb2003]

Sorry, just realised this is a duplicate of #3. I should check before I submit a PR. 🤦