yaafe-core: support debug-only stderr output: DBLOG, DBLOG_IF
yaafe-io: fix mem leaks on Smarc, MP3FileReader: support TimeStart,
TimeLimit, TrimBeginningSilence
src_python: fit doctest; add trim_beginning_silence, time_start, time_limit
in FeaturePlan
add example of using time_start, time_limit
Merge branch 'master' of github.com:mckelvin/Yaafe