issue 301: osx debug build error
android: remove -pg flag to avoid link error
set initial clock value if media start time is not 0
packed yuv format is not supported by opengl now
subtitle: player level logic is common
qml: support ass subtitle
uninstall filters in target dtor and ~Filter
qml ass subtitle item update less if no image

TODO:
update only if image changed
better way to get ffmpeg supported subtitle extensions
subtitle: search dirs support
subtitle: add signal loaded(path)
qml subtitle image fillMode
update plugins.qmltypes
added support for avdevice by forcing input format
support both ffmpeg/libav for debian package
add -dbg to debian packages
clean qmake detection on debian package clean rule