Unbreak build on FreeBSD

[jbeich]

alsa-plugins contains OSS plugin which is natively supported on DragonFly, FreeBSD and Solaris. Let's follow cpal. Runtime tested via FishFight (package).

$ cargo build
[...]
error[E0432]: unresolved import `snd`
  --> src/lib.rs:32:9
   |
32 | pub use snd::{AudioContext, Sound};
   |         ^^^ use of undeclared crate or module `snd`
   |
help: there is a crate or module with a similar name
   |
32 | pub use std::{AudioContext, Sound};
   |         ~~~

[not-fl3]

Thanks!