Dynamic loading logic copied from https://github.com/neon-bindings/neon/tree/0.10.0/crates/neon-runtime/src/napi/bindings.
Tiny binding to libuv, that does not link to the library. The expectation is that the consumer will link to the appropriate library.
Essentially just a rust version of uv.h, to provide interfaces without making
decisions on how to provide the actual implementation. This is similar to
napi-sys.