Rust XCB `xcb::Connection::connect_to_fd*` functions violate I/O safety

Summary

The API of `xcb::Connection` has constructors which allow an arbitrary `RawFd` to be used as a socket connection. On either failure of these constructors or on the drop of `Connection`, it closes the associated file descriptor. Thus, a program which uses an `OwnedFd` (such as a `UnixStream`) as the file descriptor can close the file descriptor and continue to attempt using it or close an already-closed file descriptor, violating I/O safety. Starting in version 1.6.0, `xcb` provides `Connection::connect_with_fd` and `Connection::connect_with_fd_and_extensions` as safe alternatives and deprecates the problematic functions.