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
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.
add qt include and lib dir to config test
Merge pull request #245 from wang-bin/gl

OpenGL better structure and performance
gl: qt4 and gles2 build fix. move glActiveTexture to helper
windows link error

nested class in exported class must be exported?
build ffmpeg: gpl v3, x86, change android lib name
ci: parallel build and download

can not install pxz. parallel command error
gl: shader is associated with context
dptr base class default ctor
sg: use opengl. default is disabled. crash now
Merge remote-tracking branch 'origin/master'