3rd try to get the loop filter ref/mv check working correctly.
Fixes at least:
src19td.IBP.264
CVWP3_TOSHIBA_E.264
cvmp_mot_picaff0_full_B.26l
CVMP_MOT_FRM_L31_B.26l
cvmp_mot_frm0_full_B.26l
CVMP_MOT_FLD_L30_B.26l
cvmp_mot_fld0_full_B.26l

Originally committed as revision 14337 to svn://svn.ffmpeg.org/ffmpeg/trunk
