- Added support to read from stdin if the file source is "stdin"

[SeanTasker]

I wanted to playback recordings of raw channels so I could easily iterate and compare results in my software. I just use cat to pipe to pv to throttle the playback at an approximate real time speed through to stdin for ODAS using the provided PR.

cat rawdump-48k32bit8chan | pv -L 1500k | ./build/odas/bin/odaslive -c odas-config/stdin-subbi-postfilter.cfg