sndfile actually supports reading and writing from/to stdin/out with the -
filename, so allow that.
Add support for streaming in dsf, dff and midifile as well.
Add a -a option to pw-cat use a pipe with raw bytes, otherwise try to
use the parsers and sndfile to read/write from/to stdin/stdout.
You can then do things like:
sox 2L-053_04_stereo-DSD64.dff -t dsf - | pw-cat -pdv -
pw-cat 07.Joe.Satriani.Clouds.race.across.the.sky.wav | pw-cat -pv -
pw-cat -rmv --target=0 - | pw-mididump -
Fixes: #4204
