Check if dxva2api.h is recent enough to compile vc1_dxva2_hwaccel.

Originally committed as revision 21444 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1234,7 +1234,7 @@ tiff_encoder_suggest="zlib"
 truehd_decoder_select="mlp_decoder"
 tscc_decoder_select="zlib"
 vc1_decoder_select="h263_decoder"
-vc1_dxva2_hwaccel_deps="dxva2api_h"
+vc1_dxva2_hwaccel_deps="dxva2api_h DXVA_PictureParameters_wDecodedPictureIndex"
 vc1_dxva2_hwaccel_select="dxva2 vc1_decoder"
 vc1_vaapi_hwaccel_deps="va_va_h"
 vc1_vaapi_hwaccel_select="vaapi vc1_decoder"
@@ -2425,6 +2425,8 @@ check_header vdpau/vdpau.h
 check_header vdpau/vdpau_x11.h
 check_header X11/extensions/XvMClib.h
 
+check_struct dxva2api.h DXVA_PictureParameters wDecodedPictureIndex
+
 if ! enabled_any memalign memalign_hack posix_memalign malloc_aligned &&
      enabled_any $need_memalign ; then
     die "Error, no aligned memory allocator but SSE enabled, disable it or use --enable-memalign-hack."