Do not suggest to use gas-preprocessor if using it would break compilation.

gas-preprocessor does not work on ppc with pic and on ppc64.
Forward interlaced field information from mov to ffv1 decoder.

Only read the information for old ffv1, level/version 3 saves
the information in the bitstream.
Fixes a part of ticket #2190.

Signed-off-by: Carl Eugen Hoyos <cehoyos@ag.or.at>
Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  Forward interlaced field information from mov to ffv1 decoder.
  Do not suggest to use gas-preprocessor if using it would break compilation.

Merged-by: Michael Niedermayer <michaelni@gmx.at>