Default is to utilize provided openal-soft library if possible
and if not overridden by property 'joal.openal.lib'.
Hence returning ALFactory.PREFER_SYSTEM_OPENAL (default: false)
This also resolves issues w/ OSX El Capitan 10.11,
which provides OpenAL via 'openal' library name (same as openal-soft)
and causes stuttering w/ GLMediaPlayer's ALAudioSink!
Fixed as described
ALAudioSink: DEBUG: Show OpenAL Version