Implement Send on everything

[kovaxis]

Hello.
I've noticed that MidiOutputConnection implements Send, and it's quite a useful feature.
However, other structs don't seem to implement it, which surprised me because MidiInputConnection is used only as a token to keep the connection alive.
Is it possible to make input connections, and for that matter the rest of the structs, implement Send, or am I missing something important that disallows this?

[Boddlnagg]

Actually I had already added a comment that all the structs should implement Send:

midir/src/common.rs

Line 10 in 5e90714

// TODO: make sure that these structs are all `Send` and implement `Debug` (?)

I've only done it for MidiOutputConnection consistently on all the backends so far, because I needed that for one of the examples. Ideally I would want to be 100% sure that sending midi connections to other threads is actually supported by all the backends, but I don't really know of any reason why it shoudn't.

So I'm definitely going to look into this soon. Thanks for the report!

[Boddlnagg]

This has been fixed by #38