gl: VideoShader class
Merge branch 'master' into gl
qml: sg node. not finished
color transformation supports in/out color space. add rgb

TODO:
other color spaces(XYZ, ...)
recompute matrix if ion/out color space changed
gl: always use qt's shader classes to avoid resolving gl symbols

glGetUniformLocation may be not declared in std gl headers
Merge branch 'master' into gl
gl: compute color matrix including yuv->rgb in cpu
gl: use planar shader. supports rgb
build: use av_frame_alloc instead of deprecated avcodec_alloc_frame

also used in LibAVFilter
build avfilter with old version. but may not work

ffmpeg2.2 can work with deprecated api (set
QTAV_HAVE_av_buffersink_get_frame=0). ffmpeg1.1.3 crash
build with libav and ffmpeg>=0.11

avfilter does not work: ffmpeg 0.11 1.1, 1.2
libav crash
use default av callback if set null to avoid libav crash. issue 239
vaapi: dynamic load va-x11 and va-gl

TODO: system may have no x11, so x11 should dynamically load too
use qopengl.h instead of gl.h? check glx or gles and use va-egl
vaapi: dynamic load x11. use qt opengl header
Merge pull request #240 from wang-bin/va

va: dynamic load va and x11 libs to let vaapi work on variant evironments
gl: VideoShader
osx: add vda support

TODO: sse4
vda: sse4 copy. fix crash if vda not support
va: remove useless parameter. fix vaapi crash when seeking

can not set ctx pixel format other than VAAPI_VLD.