openh264dec: Try to handle frame reordering
openh264dec: Try to handle frame reordering

As openh264 has no way to attach any IDs to input frames that we then get on
the output frames, we have to assume that the input has valid PTS. We just
take the frame with the oldest PTS, and if there is no PTS information we take
the one with the oldest DTS.

deepikateriar/openwebrtc-plugins-0.80,sancane/openwebrtc-gst-plugins,ossy-szeged/openwebrtc-gst-plugins,ford-prefect/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,ford-prefect/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,deepikateriar/openwebrtc-plugins-0.80,EricssonResearch/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,EricssonResearch/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.8,ossy-szeged/openwebrtc-gst-plugins,EricssonResearch/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.80,ford-prefect/openwebrtc-gst-plugins,deepikateriar/openwebrtc-plugins-0.80,sancane/openwebrtc-gst-plugins,ossy-szeged/openwebrtc-gst-plugins,ossy-szeged/openwebrtc-gst-plugins,ford-prefect/openwebrtc-gst-plugins,sancane/openwebrtc-gst-plugins