`pipe()` isn't used since 15927b6511bc8304ae144a45c9fbfca88e5dd641,
and `socketpair()` from `#include <sys/socket.h>` is used only in the
examples. In practice, you can use probably also use anything that
allows you to create fd pairs, such as named pipes or anonymous pipes.
We use the cross-platform GstPollFD API in the plugin.