Change the fixed triple buffering swapchain to a pool based implementation
this should provide a clearer view about who owns which buffer at what time,
a buffer is either in the pool, in rendering or attached to a QSGNode
This may also avoid some racy scenarios where the framebuffers are released by
VLC while still in used by Qt, the pool exists as long as some buffers are
referencing it
Change the fixed triple buffering swapchain to a pool based implementation
this should provide a clearer view about who owns which buffer at what time, a buffer is either in the pool, in rendering or attached to a QSGNode
This may also avoid some racy scenarios where the framebuffers are released by VLC while still in used by Qt, the pool exists as long as some buffers are referencing it
Note that this branch contains commits from #12