remove some finished TODO
libav: add missing header
component id must be defined even if component is disabled
use libav avresample if ffmpeg resampler disabled

TODO:
if null, crash
use QGLWidge::renderText() to render osd

TODO:
1.gl viewport rect should be vo rect. otherwise text outside viewport
will not display.
2.render without QGLWidget
set gl viewport to widget rect to display text correctly
gl: always clear color buffer to avoid flicker
gl: try draw array
fix build issues
enable/disable audio
player: enable/disable audio
player: auto hide control bar
player: ao option
use QTAV_HAVE() macro
GL ES2 works
gl: fix color format
gl: fix no picture on the 2nd time change to es2
gl: correct aspect ratio for GL ES2

BUG:
frame will not show until manually resized
TODO:
setupAspectRation for fixed pipeline
gl: use the same tex coord array
gl: fix draw mode