vo_corevideo: restructure this video output
Restructure this video output to be similar to vo_gl, even if simpler
and less feature complete (for example it's still missing EOSD
support). Ideally, it should act as a decent fallback in the case
where something breaks in the OSX support of vo_gl.
Here's a summary of what changed:
* Remove the shared buffer code since it wasn't using any function
from the CoreVideo API. Moreover, its presence in vo_corevideo was
forcing the non-GUI related code to perform more image copies than
necessary. Equivalent shared-buffer functionality will be added in
a separate new VO in the next commit (this means OSX GUIs will need
to specify a different VO).
* Clean up the code to conform a bit more to the mplayer2
conventions. Enforce 80 column wrapping, use a private struct for
file variables, use the new libvo api.
* Add OSD rendering using OpenGL instead of writing directly on the
video image data.
* Simplify the logic for the rendering function when dealing with
panscan.
* Add VOCTRL_REDRAW_FRAME support.
* Add colormatrix support by using the built-in API provided by
CoreVideo.