Add FFMPEG_ prefix to all multiple inclusion guards.

Originally committed as revision 10765 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/fifo.h

@@ -21,8 +21,8 @@
  * A very simple circular buffer FIFO implementation.
  */
 
-#ifndef FIFO_H
-#define FIFO_H
+#ifndef FFMPEG_FIFO_H
+#define FFMPEG_FIFO_H
 
 #include <stdint.h>
 
@@ -99,4 +99,4 @@ static inline uint8_t av_fifo_peek(AVFifoBuffer *f, int offs)
         ptr -= f->end - f->buffer;
     return *ptr;
 }
-#endif /* FIFO_H */
+#endif /* FFMPEG_FIFO_H */