open-gop patch for x264 (committed)

[G_M_C]

If, for technical reasons, we still need to force IDR frames every once in a while despite open-GOPs being perfectly fine keyframes, the value should be really large.

only 1 IDR is needed in a stream.

If add these up, then the vanue DS is speaking of, could be set eqqual to the number of frames in the input-stream ? If you then make first frame of the output-stream an IDR, you wont get another one (if not needed/requested).