Make all tools output to stdout (pw-mon mostly) so that we can pipe the
output around.
Send errors to stderr.
fprintf(stdout, ...) -> printf(...)
setlinebuf for stdout so that pipe works better.
See #2110
Just like the real free() we should just ignore a NULL pointer, makes the
caller code easier for those instances where properties are optional.
Patch generated with concinelle with a few manual fixes.
Sends the captured data from a source directly to a sink.
It uses an input and output stream so the source and sink can be
moved in pavucontrol, channel remixing is possible and the volume
can be adjusted.
See #959
