BlockingQueue: block for full/empty separately
fix seeking error if audio stream not exists
playing music support. fix crash problem for audio stream
renderer: black background. focus(key events), move/resize if no parent.
ignore if pause state not changed
tests: shared renderer for 2 players

BUG: event filter only works for the last player
add Changelog
misc
update copyright date
Clock can be auto selected or force setted

auto: using audio clock if audio stream found
capture video in main thread or another thread is selectable. api change
capture: error code, pause avthread if in main thread, rm dead code
add seek interval limitation to avoid seeking too frequently
update frames when seeking on pause. ugly code
slow down volume change if it,s small
add network test
README: looks good
README
ipp