libavcodec/xsubenc.c: Fix bounding box coordinates

Fix coordinates of the lower right corner of the text area.
Note that the coordinates are redundant as the size and
position of the text area are known.
Many decoders (including Sony Playstation 3, VLC and FFmpeg)
ignore the redundant coordinates.
Some hardware decoders need them for correct playback.

Verified on Philips DVD player models HTS7201 and DVP3380.

Fixes ticket #3031
Signed-off-by: Erik Olofsson <eaj.olofsson@gmail.com>
Reviewed-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/xsubenc.c

@@ -166,8 +166,8 @@ static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
     bytestream_put_le16(&hdr, height);
     bytestream_put_le16(&hdr, h->rects[0]->x);
     bytestream_put_le16(&hdr, h->rects[0]->y);
-    bytestream_put_le16(&hdr, h->rects[0]->x + width);
-    bytestream_put_le16(&hdr, h->rects[0]->y + height);
+    bytestream_put_le16(&hdr, h->rects[0]->x + width -1);
+    bytestream_put_le16(&hdr, h->rects[0]->y + height -1);
 
     rlelenptr = hdr; // Will store length of first field here later.
     hdr+=2;