match new API of serialport-rs 2.0.0

[ndusart]

Prepare the changes to be made to use the next release of serialport-rs:

• termios crate was replaced by nix, so replacing it here as well
• libc is taken from nix crate, it avoid to use a different version than what nix is using.
• available_baud_rates is removed in favor of BaudRate::platform_rates() so removing the pub use
• defined a new Result and Error type (just reexporting the ones from serialport-rs), it's for having some conversion trait for nix::Error since we're using nix now and termios functions returns this kind of error instead of io::Error

The downside is that Cargo.toml is now referencing git repositories instead of published versions.
Maybe you'll want to wait for the release of serialport-rs before merging.

[berkowski]

Good to see serialport-rs is chugging along nicely. I'm traveling around for the next few days and will check out the PR once settled again

[berkowski]

Alright, I've had some time finally to look at this. Thanks for the PR!

Switching over to nix raises some new issues on a few build targets, and the current head serialport-rs seems to have some issues on OSX itself. Because of that I'd like to have your changes pushed to a new working branch (which I'll create) if that's OK with you. Once the nix and serialport-rs issues are resolved we can have a clean merge back onto master.

[ndusart]

Of course we can push these changes into a new branch.

The breakages seem to be:

• for OSX 32 bits: https://github.com/dcuddeback/iokit-sys/blob/master/src/types.rs is missing some use statement for vm_address_t (I do not know where these should come from though, maybe a typo and it's mach_vm_address_t as well ?) and mach_vm_size_t (opened Cannot build for i686-apple-darwin dcuddeback/iokit-sys#4)
• for OSX 64 bits (and probably 32 bits as well): it is certainly that version of libc taken by nix (from github) does not match with the one taken by IOKit-sys (from crates.io), hence the mismatch in types, we can probably only fix this when we can rely on released version of nix and serialport-rs.
• for BSD platforms, nix::poll is not available in all platforms, it's pretty close to be fixed as you saw when opening your PR there.

[berkowski]

Great. And thanks for your work on all the upstream crates like nix and libc! Please switch your PR target to the new serialport-2 branch and we'll go from there.

[berkowski]

freebsd targets are now passing since your nix-rust/nix#672 was accepted, so that's one down. I'm going to go ahead and merge this. Thanks!