avcodec/mpeg4videoenc: Use 64 bit for times in mpeg4_encode_gop_header()

Fixes truncation
Fixes Assertion n <= 31 && value < (1U << n) failed at libavcodec/put_bits.h:169
Fixes: ffmpeg_crash_2.avi

Found-by: Thuan Pham <thuanpv@comp.nus.edu.sg>, Marcel Böhme, Andrew Santosa and Alexandru RazvanCaciulescu with AFLSmart

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
void ff_mpeg4_encode_video_packet_header(MpegEncContext *s)
{
    int mb_num_bits = av_log2(s->mb_num - 1) + 1;

    put_bits(&s->pb, ff_mpeg4_get_video_packet_prefix_length(s), 0);
    put_bits(&s->pb, 1, 1);

    put_bits(&s->pb, mb_num_bits, s->mb_x + s->mb_y * s->mb_width);
    put_bits(&s->pb, s->quant_precision, s->qscale);
    put_bits(&s->pb, 1, 0); /* no HEC */
}

void ff_mpeg4_encode_video_packet_header(MpegEncContext *s)
{
    int mb_num_bits = av_log2(s->mb_num - 1) + 1;

    put_bits(&s->pb, ff_mpeg4_get_video_packet_prefix_length(s), 0);
    put_bits(&s->pb, 1, 1);

    put_bits(&s->pb, mb_num_bits, s->mb_x + s->mb_y * s->mb_width);
    put_bits(&s->pb, s->quant_precision, s->qscale);
    put_bits(&s->pb, 1, 0); /* no HEC */
}
