avcodec/utils: Fix encoder allocation size

Fixes Ticket2645
Found-by: Darrell Walisser
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 175e916fa2)

Conflicts:
	libavcodec/utils.c

libavcodec/utils.c

@@ -474,7 +474,7 @@ static int video_get_buffer(AVCodecContext *s, AVFrame *pic)
 
             buf->linesize[i] = picture.linesize[i];
 
-            buf->base[i] = av_malloc(size[i] + 16); //FIXME 16
+            buf->base[i] = av_malloc(size[i] + 16 + STRIDE_ALIGN - 1); //FIXME 16
             if (buf->base[i] == NULL)
                 return AVERROR(ENOMEM);