pictordec: decode 1bpp / 4bpp images when extra header marker is missing

based on 56f6628b

samples:

http://www.datafilehost.com/download-94b5bc1b.htmlReviewed-and-Tested-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pictordec.c

@@ -133,7 +133,7 @@ static int decode_frame(AVCodecContext *avctx,
         return AVERROR_INVALIDDATA;
     }
 
-    if (bytestream2_peek_byte(&s->g) == 0xFF || bpp == 8) {
+    if (bytestream2_peek_byte(&s->g) == 0xFF || bpp == 1 || bpp == 4 || bpp == 8) {
         bytestream2_skip(&s->g, 2);
         etype = bytestream2_get_le16(&s->g);
         esize = bytestream2_get_le16(&s->g);