doc/examples/extract_mvs: add motion information

Note that the motion information includes subpel motion information

This was likely forgotten in 56bdf61baa.

Tested:
```
$ make examples -j
...
$ doc/examples/extract_mvs in.264 | head -40 | \
    csvcut -C framenum,source,flags |csvlook
| blockw | blockh |  srcx | srcy |  dstx | dsty | motion_x | motion_y | motion_scale |
| ------ | ------ | ----- | ---- | ----- | ---- | -------- | -------- | ------------ |
|     16 |     16 |    20 |   26 |     8 |    8 |       49 |       72 |            4 |
|     16 |     16 |   152 |   15 |   136 |    8 |       65 |       28 |            4 |
|     16 |      8 |   360 |    3 |   360 |    4 |        1 |       -6 |            4 |
|     16 |      8 |   360 |   13 |   360 |   12 |       -1 |        4 |            4 |
|     16 |     16 |   440 |   10 |   440 |    8 |        3 |       10 |            4 |
|      8 |     16 |   829 |    7 |   836 |    8 |      -31 |       -6 |            4 |
|      8 |     16 |   844 |    7 |   844 |    8 |       -1 |       -4 |            4 |
|     16 |     16 | 1,004 |   14 | 1,048 |    8 |     -177 |       24 |            4 |
|     16 |     16 | 1,096 |    8 | 1,096 |    8 |       -1 |        0 |            4 |
|     16 |      8 | 1,417 |   24 | 1,416 |    4 |        7 |       82 |            4 |
|     16 |      8 | 1,416 |   13 | 1,416 |   12 |        0 |        6 |            4 |
|     16 |      8 |    87 |   20 |    88 |   20 |       -7 |        0 |            4 |
|     16 |      8 |    99 |   44 |    88 |   28 |       45 |       66 |            4 |
...
```

Also:
```
$ make fate -j
...
```

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

doc/examples/extract_mvs.c

@@ -61,10 +61,11 @@ static int decode_packet(const AVPacket *pkt)
                 const AVMotionVector *mvs = (const AVMotionVector *)sd->data;
                 for (i = 0; i < sd->size / sizeof(*mvs); i++) {
                     const AVMotionVector *mv = &mvs[i];
-                    printf("%d,%2d,%2d,%2d,%4d,%4d,%4d,%4d,0x%"PRIx64"\n",
+                    printf("%d,%2d,%2d,%2d,%4d,%4d,%4d,%4d,0x%"PRIx64",%4d,%4d,%4d\n",
                         video_frame_count, mv->source,
                         mv->w, mv->h, mv->src_x, mv->src_y,
-                        mv->dst_x, mv->dst_y, mv->flags);
+                        mv->dst_x, mv->dst_y, mv->flags,
+                        mv->motion_x, mv->motion_y, mv->motion_scale);
                 }
             }
             av_frame_unref(frame);
@@ -166,7 +167,7 @@ int main(int argc, char **argv)
         goto end;
     }
 
-    printf("framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags\n");
+    printf("framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags,motion_x,motion_y,motion_scale\n");
 
     /* read frames from the file */
     while (av_read_frame(fmt_ctx, pkt) >= 0) {