Bug caused by integer overflow in ffmpeg_generic_seek_workaround().
Function max_ii() was used to limit int_64tvalue.
After fixing the issue there was another issue, where near-infinite loop
was caused by requested_pos being very large and stream being cut in a
way, that it was missing keyframe at beginning.
This was fixed by checking if we are reading beyond file content.
Reviewed By: zeddb
Differential Revision: https://developer.blender.org/D11888
118946d195