flashsv: use skip_bits_long() where required

skip_bits(gb, n) with n > 17 doesn't work with all bitstream readers.
Switch to skip_bits_long() instead.

Originally committed as revision 15930 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/flashsv.c

@@ -211,7 +211,7 @@ static int flashsv_decode_frame(AVCodecContext *avctx,
                     /* return -1; */
                 }
                 copy_region(s->tmpblock, s->frame.data[0], s->image_height-(hp+hs+1), wp, hs, ws, s->frame.linesize[0]);
-                skip_bits(&gb, 8*size);   /* skip the consumed bits */
+                skip_bits_long(&gb, 8*size);   /* skip the consumed bits */
             }
         }
     }