picture: ensure the new seq header and op param info flags are attached to the...
picture: ensure the new seq header and op param info flags are attached to the next visible picture in display order
If the first picture in coding order after a new sequence header is parsed is not visible, the first picture output by dav1d after the fact (which is coded after the aforementioned invisible picture) would not trigger the new seq header event flag as expected, despite being the first containing a reference to a new sequence header.
Assuming the invisible picture is ever output, the result of this change will be two pictures signaling a new sequence header was seen despite there being only one new sequence header.
Fixes #394 (closed).