allow progressive buffering for first fragment in case HLSSettings.startFromLevel=-1 and there is only one level
related to https://github.com/mangui/flashls/issues/77
ChromelessPlayer.as: reduce onPosition() ExternalInterface call overhead by transmitting only one args
also only update min/mwax/low buffer len upon player starting/value modification to reduce call overhead
add comment
update swf/swc