avutil/mathematics: Document av_rescale_rnd() behavior on non int64 results
Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit e154353fdb
)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>