lavc/libopenjpegdec: support interlaced layout

Fixes tickets #1102.

Interlaced layout is supported thought use of codec extradata:
  avctx->extradata[0] enables interlaced layout,
  avctx->extradata[1] stores field order.
lavf/mxfdec: support segmented frame layout as separate field layout

According to S377M, segmented frame layout is identical to separate
field layout except that the two fields are taken from a single scan
of the incoming image, ie: they are coincident in time. Thus the
resulting frame is progressive.
lavf/mxfdec: support j2k codec with separate/segmented fields layout
lavf/mxfdec: fix codec and stream time base for separate/segmented fields layout

Since two packets are required to decoded a frame, we need to divide by
a factor of 2 the stream time base so output ptses are correct.
lavf/mxfdec: add j2k codec to intra only codecs
lavf/mxfdec: add -field_rate option

Interpret sample rate as field rate for separate/segmented fields layout.
lavf/mxfdec: generate ptses for interlaced j2k streams

Packet ptses correspond to frame numbers. This plus dividing by a factor
of 2 the stream time base will output correct ptses for decoded frames
since we need 2 packets for one decoded frame.