avfilter: make avfilter_default_free_video_buffer() static

This function is not referenced outside this file and has no
prototype.  Feel free to flame if this is wrong.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@22314 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavfilter/defaults.c

@@ -23,7 +23,7 @@
 #include "avfilter.h"
 
 /* TODO: buffer pool.  see comment for avfilter_default_get_video_buffer() */
-void avfilter_default_free_video_buffer(AVFilterPic *pic)
+static void avfilter_default_free_video_buffer(AVFilterPic *pic)
 {
     av_free(pic->data[0]);
     av_free(pic);