* Reuse std::io::Error for raw *nix errno
This commit removes custom `yanix::Errno` and instead (as was
previously suggested) reuses `std::io::Error` to generate and wrap
raw *nix errno value.
* Update wasi-common to use new Yanix error type
This commit updates `wasi-common` to use new way of handling raw
OS error in `yanix`; i.e., via re-use of `std::io::Error` instead
of a custom `Errno` enum.
* Fix formatting
* Unwrap if io::Error created from raw OS error
This commit calls `unwrap` on `err` if that one was created via
`io::Error::last_os_error()`. It also refactors error matching
in several syscalls on the BSD platform (mainly).
* Add yanix crate
This commit adds `yanix` crate as a Unix dependency for `wasi-common`.
`yanix` stands for Yet Another Nix crate and is exactly what the name
suggests: a crate in the spirit of the `nix` crate, but which takes a different
approach, using lower-level interfaces with less abstraction, so that it fits
better with its main use case, implementation of WASI syscalls.
* Replace nix with yanix crate
Having introduced `yanix` crate as an in-house replacement for the
`nix` crate, this commit makes the necessary changes to `wasi-common`
to depend _only_ on `yanix` crate.
* Address review comments
* make `fd_dup` unsafe
* rename `get_fd` to `get_fd_flags`, etc.
* reuse `io::Error::last_os_error()` to get the last errno value
* Address more comments
* make all `fcntl` fns unsafe
* adjust `wasi-common` impl appropriately
* Make all fns operating on RawFd unsafe
* Fix linux build
* Address more comments
