Move av_fast_{m,re}alloc from lavc to lavu.

libavcodec/avcodec.h

@@ -36,6 +36,10 @@
 #include "libavutil/dict.h"
 #include "libavutil/frame.h"
 #include "libavutil/log.h"
+#if FF_API_FAST_MALLOC
+// to provide fast_*alloc
+#include "libavutil/mem.h"
+#endif
 #include "libavutil/pixfmt.h"
 #include "libavutil/rational.h"
 
@@ -4197,27 +4201,6 @@ AVBitStreamFilter *av_bitstream_filter_next(AVBitStreamFilter *f);
 
 /* memory */
 
-/**
- * Reallocate the given block if it is not large enough, otherwise do nothing.
- *
- * @see av_realloc
- */
-void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
-
-/**
- * Allocate a buffer, reusing the given one if large enough.
- *
- * Contrary to av_fast_realloc the current buffer contents might not be
- * preserved and on error the old buffer is freed, thus no special
- * handling to avoid memleaks is necessary.
- *
- * @param ptr pointer to pointer to already allocated buffer, overwritten with pointer to new buffer
- * @param size size of the buffer *ptr points to
- * @param min_size minimum size of *ptr buffer after returning, *ptr will be NULL and
- *                 *size 0 if an error occurred.
- */
-void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
-
 /**
  * Allocate a buffer with padding, reusing the given one if large enough.
  *