/* the original and resized picture lists in an RrImageSet are kept ordered
as newest to oldest. we don't have timestamps for them, so we cannot
preserve this in the merged RrImageSet exactly. a decent approximation,
/* the original and resized picture lists in an RrImageSet are kept ordered
as newest to oldest. we don't have timestamps for them, so we cannot
preserve this in the merged RrImageSet exactly. a decent approximation,