add #include so make checkheaders passes

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@23637 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavfilter/vsrc_buffer.h

@@ -19,6 +19,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "avfilter.h"
+
 int av_vsrc_buffer_add_frame(AVFilterContext *buffer_filter, AVFrame *frame,
                              int64_t pts, AVRational pixel_aspect);