Merge branch 'develop' into io
src/io/source_apple_audio.{c,h}: if samplerate = 1, use actual source one
src/io/source.h: add get_samplerate
Merge branch 'develop' into io
src/io/source_sndfile.{c,h}: add get_samplerate, if == 1 use file samplerate
Merge branch 'develop' into io
interfaces/python/demo_source.py: use source samplerate
examples/utils.c: improve error message if no input found
examples/utils.c: exit if an output file could not be opened
merge from develop