mpegvideo: Remove a leftover function declaration

Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/mpegvideo_common.h

@@ -41,12 +41,6 @@
 
 int dct_quantize_c(MpegEncContext *s, DCTELEM *block, int n, int qscale, int *overflow);
 
-/**
- * Allocate a Picture.
- * The pixels are allocated/set by calling get_buffer() if shared = 0.
- */
-int alloc_picture(MpegEncContext *s, Picture *pic, int shared);
-
 /**
  * Set the given MpegEncContext to common defaults (same for encoding and decoding).
  * The changed fields will not depend upon the prior state of the MpegEncContext.