* include/vlc_block_helper.h: small bugfix to block_FindStartcodeFromOffset().
* modules/packetizer/mpegvideo.c: get aspect ratio for MPEG2 video streams (still needs to be done for MPEG1).
* modules/codec/libmpeg2.c: use p_dec->fmt_in.video.i_aspect if available.
* modules/stream_out/transcode.c, modules/codec/ffmpeg/encoder.c: respect aspect ratio during transcoding.