h264, h265: raise MaxNALUSize

[database64128]

When streaming a 50Mbps 2160p60 HEVC video encoded by AMD AMF from OBS via RTMP, none of the frames can get through:

unable to decode AVCC: NALU size (3497231) is too big, maximum is 3145728

Reducing the resolution to 1440p allows most of the frames to get through, but the same error still appears about once every 15 minutes:

unable to decode AVCC: NALU size (3464043) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3463992) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3463991) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3417504) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3417342) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3372157) is too big, maximum is 3145728
unable to decode AVCC: NALU size (3314591) is too big, maximum is 3145728

Raising the size limit to 4 MiB seems to have resolved the issue for me. Updated the comment as well.

[aler9]

Thanks for your tests, adding limits is required in order to prevent RAM exhaustion-based attacks but nothing prevents to update them. Merged.