This uses the same line sweep algorithm originally created to copy DXGI
textures to IVSHMEM to implement the copy from IVSHMEM to memory-mapped
pixel buffer objects.
The way things were handled in EGLTexture is not only very hard to
follow, but broken. This change set breaks up EGLTexture into a modular
design making it easier to implement the various versions.
Note that DMABUF is currently broken and needs to be re-implemented.