x264enc: Auto-detect interlace mode from caps
x264enc: Auto-detect interlace mode from caps

If the caps are interlaced, interlacing is always enabled on the
encoder. If the interlace-mode field is missing or if it's progressive,
the encoder uses the "interlaced" property.

https://bugzilla.gnome.org/show_bug.cgi?id=775228

GrokImageCompression/gst-plugins-ugly,GStreamer/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,GStreamer/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,GStreamer/gst-plugins-ugly,StreamUtils/gst-plugins-ugly