CrystalHD: Improve interlaced h.264 support.

As previously discussed, the CrystalHD hardware returns exceptionally
useless information about interlaced h.264 content - to the extent
that it's not possible to distinguish MBAFF and PAFF content until
it's too late.

This change introduces use of the h264_parser to help bridge the
gap; it can indicate if the input data is PAFF fields or not.

With this clarity, some of heuristics can be removed from the code,
making this less convoluted.

Finally, I found an MBAFF clip that acts like non h.264 content so
I had to make allowances for that.

Note that I still cannot distinguish between two forms of PAFF,
where the hardware either returns individual fields or a field-pair.
It's not clear that there's even a spec relevant difference between
the two forms, as opposed to hardware ideosyncracies.

configure

@@ -1276,7 +1276,7 @@ h263_vaapi_hwaccel_select="vaapi h263_decoder"
 h263i_decoder_select="h263_decoder"
 h263p_encoder_select="h263_encoder"
 h264_decoder_select="golomb h264dsp h264pred"
-h264_crystalhd_decoder_select="crystalhd h264_mp4toannexb_bsf"
+h264_crystalhd_decoder_select="crystalhd h264_mp4toannexb_bsf h264_parser"
 h264_dxva2_hwaccel_deps="dxva2api_h"
 h264_dxva2_hwaccel_select="dxva2 h264_decoder"
 h264_vaapi_hwaccel_select="vaapi"