vda: fix chroma issue with vda upload

GL_YCBCR_422_APPLE need a GL_RGB internal format not GL_RGBA
vda: cvref textures are non power of two so don't allocate extra space
vda: use IOSurfaceGetPixelformat instead of CVPixelBufferGetPixelFormatType

We have converted the texture to an IOSurfaceRef so use that to check
for format.
vda: allocate pot texture if requested
vda: re-enable cvref upload on osx 10.9.4 since it seem to work there
cvref: retain reference before releasing old

if we re-add same surface to renderer we could end up freeing texture
before retaining reference.
cvref: skip upload of texture by looking at flipindex

The texture can be in use for a while after this call.
Merge pull request #12 from elupus/removevda

Fixes for CVREF rendering on osx