allocate 32 extra bytes at the end of the probe buffer and remove most probe buf_size checks

Originally committed as revision 8677 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/tta.c

@@ -29,8 +29,6 @@ typedef struct {
 static int tta_probe(AVProbeData *p)
 {
     const uint8_t *d = p->buf;
-    if (p->buf_size < 4)
-        return 0;
     if (d[0] == 'T' && d[1] == 'T' && d[2] == 'A' && d[3] == '1')
         return 80;
     return 0;