`pipe()` isn't used since 15927b6511,
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.
ipcpipeline1 is a very simple test that shows a short videotestsrc fragment.
ipc-play is a clone of gst-play that splits the pipeline in two
processes, running the source & demuxer on the master process
and the decoders & sinks on the slave.
