Enable debug variable only when debug code is enabled, fixes the warning:

rtp_h264.c: In function ‘h264_handle_packet’:
rtp_h264.c:168: warning: unused variable ‘data’

Originally committed as revision 10923 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtp_h264.c

@@ -165,7 +165,9 @@ static int h264_handle_packet(RTPDemuxContext * s,
                               const uint8_t * buf,
                               int len)
 {
+#ifdef DEBUG
     h264_rtp_extra_data *data = s->dynamic_protocol_context;
+#endif
     uint8_t nal = buf[0];
     uint8_t type = (nal & 0x1f);
     int result= 0;